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MG Midget and Sprite Technical Gearbox Refurbishment BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - Gearbox Refurbishment
| I'm about to embark on my first gearbox re-build. I have got a kit that includes new baulk rings from Heathrow Transmissions but it looks as though I might need a few more bits and bobs.
Late last night I found a Youtube video series on gearbox refurbishment. It was episode 2 that I stumbled across and I haven't watched it all yet but it looks as though I'll need a decent, long puller to get the bearings off. However, both Haynes and the factory manual suggest that separating the bearings from the shafts is a simple matter of tapping them apart with a drift. He also recommended heating the bearings and chilling the shafts to make fitting the replacements easier but there's no mention of this in either manual. What is your experience of rebuilding gearboxes? Should I stick with the Manual methods or follow the Youtube advice? Colin |
| C Mee |
| The manual every time-
The youtube guy will probably do another one saying the first one didn't work and he'll be doing a third to correct his mistakes in the second---------- On the freezing/heating thing--freezing the shafts doesn't make much difference at all but with the bearings a nice pot of boiling hot water and let the bearings suck the heat up for a few mins. and you'll find the bearing will slide on easily or need very little help- Also when tapping/pressing a new bearing onto a shaft, tap/press on the inner part of the bearing not the outer which can dent the track where the balls run- willy |
| William Revit |
| Rebuilt my box last week with the same kit as the one you have bought. The best Youtube video is the one that is in three parts. I needed a thicker shim for the lay gear and a new pilot bearing for the flywheel. The reason for my rebuild was a rumbling front bearing so I didn't dismantle the tail and remote casting.
I gripped the outer race of the two big bearings in my vice and tapped the shafts out using the hide hammer for the wire wheels. I warmed the new ones in the oven to 100degs and they simply dropped on. I didn't freeze the shafts. Be certain to fit the shim at the rear bearing. Heathrow provided instructions for this. I warmed the casing with a propane blow torch and the front bearing fitted without any problems. Check the front cover plate bore and if it is worn you will have to exchange it for one with a lip seal. Refit the clutch before you start to rebuild the gear box. You can then use the first motion shaft as an alignment tool. I pulled out the old pilot bush in the flywheel using a rawbolt. The worst job was fitting the selector rods with the interlocking balls between. I have a magnetic gadget for picking up dropped screws and washers and the end fitted down the ball and plunger holes and was very useful. Eventually I managed to get the rods inserted after giving the balls a tap with a drift and hammer. Take note in the final video of the technique for replacing the rear casting. You will need to slacken the reverse fork and move the end of the selector to one side to get the casting to seat properly. The job is fiddly but not complicated. Good luck Jan T |
| J Targosz |
| Colin I think I just used a drift for bearing removal. I seem to remember Haynes being incorrect about removing the input shaft forwards. You can't as "4th" gear won't pass through the hole. So you have to remove the 3rd motion shaft (complete with 1st, 2nd and 3rd gears) backwards first, then drift the input (1st motion) shaft out, also backwards I.e. into the gearbox. |
| Bill Bretherton |
| Your right Bill. The manual refers to the smooth case box, the ribbed one comes apart as you describe. Apart from that its pretty good especially describing how the interlock plungers, detent balls and springs all go in. Make sure you have the 6 thou shims in place.These effectively pack out the gaskets. The input one often gets destroyed if the front bearing goes. They are important to prevent the main shaft moving in particular as this can lead to overselecting and jamming in 1st gear |
| Bob Beaumont |
| Hi Colin, Have you finished rebuilding the gear box? Mine is back in the car and the whirring noise has gone. There is stii noise in first and reverse but I believe this is normal. The new Heathrow synchro ring work perfectly. I now find I have to consciously push the gear leaver over to the left to select second but it is not a problem. Hope you have had sucess. Cheers Jan T |
| J Targosz |
| Making very slow progress and taking small steps, partly down to having loads of apples to press for cider production and partly due to procrastination by reading and re-reading manuals before each stage and not helped by a few days feeling rotten following my flu + Covid jabs.
I spent quite a bit of time this weekend soda blasting the paint off. I've just removed the tail shaft oil seal and realise that the internal diameter of the replacement is smaller. It was in the kit from Heathrow Transmissions so I assume it's correct but I can't see a part number on it and won't find out for sure if it's right until I have the Morris Minor box out of the Sprite and can check that it against the prop shaft. The box I'm rebuilding has the correct input shaft part number for a 1275 Sprite but could it have come off a different car with a larger diameter prop shaft? I've also found that the rear bush is worn through and, at my first attempt at removal, seems firmly fixed. Is there an easy way of removing and replacing it? There's no mention of it in either of my manuals.   |
| C Mee |
| Just taken another look and my new seal appears to have the same internal diameter as the bush behind it, so I think I'm OK there. No idea whether the old seal was actually doing anything. The bush is very reluctant to move. Will I need to cut it out? Colin |
| C Mee |
| As far as I know all the prop shaft input diameters are the same for Minors and Spridgets . the originals had a felt and oil seal. The heathrow ones appear to be just a smaller oil seal. Its not clear which bush has worn out. Do you mean the brass one in the gearbox tail extension? They generally last. Warming the case may help expand the ally and release the bush |
| Bob Beaumont |
| Thanks Bob. Yes, it's the brass bush in the gearbox extension that is completely worn through at one point near the back end. Possibly an alignment issue wherever it was used previously. |
| C Mee |
| When I fitted a midget straight cut ‘box to my A35, I couldn’t get the prop to go in. I had to take the ‘box out again, remove the rear extension and have the bush reamed to fit the prop. I didn’t own any measuring equipment in those days, so I don’t know what the difference was between them. As for the seal, as Bob says, the originals had a felt seal. I still have a few of them. |
| Dave O'Neill 2 |
| Thanks for that Dave. I already had it in mind to try the prop shaft in the re-built gearbox while it is still out on the bench. |
| C Mee |
| Colin, Might be worth a call to Heathrow Trans ? The bush on a spare casing I have looks pretty thin but could you machine up a drift with access to a lathe ? Or split with pad saw ? Heating the Ali may help getting a new one in ? Worth asking HT if a newly fitted bush needs reaming. As I said I’ve got a spare (Morry Minor) but think it’s the same part no - if you have problems you are welcome to it but the bearing has some wear ridges ! Best of luck R. |
| richard b |
| Making slow progress due to other stuff going on and only able to spend time in short stints here and there.
As you suggested, Richard, I contacted Heathrow who offered me a used bush for £25 (£6.85 from MGOC) and told me that it will need reaming. I'm hoping the folk who did my re-bore will be able to help with that. Everything is out of the casing and I'm about to start on the gear cluster. I have one mystery that maybe someone can clue me in on: I was expecting to find a needle roller bearing on the front end of the 3rd motion where it mates with the 1s motion shaft but there was nothing there - which might explain some of the lateral play in the shafts before dismantling. There was no debris in the casing. The kit from Heathrow includes a needle roller bearing which fits snugly on the spigot but is loose in the 1st motion shaft with roughly 15 thou. of lateral play. Is this normal or could it be the wrong bearing or perhaps I have a problem with the 1st motion shaft? Colin |
| C Mee |
| Hi Colin, You must keep us updated. If the intermediate roller bearing was missing from your Gearbox I don't think it would have worked. If it did it would have been very noisy and I suspect gear teeth and other parts will have been seriously damaged. How did you measure the 15 thou play. Keep in touch Jan T |
| J Targosz |
| Jan, that's the mystery.
I've never actually used this gearbox in a car, I bought it via ebay during lockdown as a replacement for the Minor box currently in my Sprite. It was painted all over and, from the dirt on it, appears to have been used like that and none of the external nuts or bolts had their paint 'seal' broken. Everything else looks to be OK with no obvious wear or damage to any of the gears. The synchro rings are worn but I don't think they are worn so badly that they didn't work. I've found a few minute unidentifiable metal specs in the casing but nothing measurable and definitely nothing that looked as though it came from a needle bearing. The 15 thou play is a estimate. The tip of a 15 thou feeler just goes into the gap, lesser feelers go in a bit further but thicker ones won't. Although measuring with a digital vernier was a bit clumsy, I still got difference of around 15 thou between the bearing's external diameter and the recess's internal diameter. |
| C Mee |
| This just doesn't look right to me. The fit on the 3rd motion shaft seems to be fine.  |
| C Mee |
| I don't see how you can measure the bearing fit with feeler gauges since the gap will be on a curve. The needles in the bearing are floating and you can only measure the OD by placing the bearing on a close fitting mandrel to align them and then using a micrometer or venier calipers to check the OD. On a used bearing I get the OD to be 0.696"so it is probably 0.700. If you insert the bearing into the first motion shaft, because the needles float, it will appear loose. I would try assembling the first and third motions shafts, with all three bearings and checking for movement.
Jan T |
| J Targosz |
| Colin the missing bearing is a mystery. As Jan says it would be a noisy box with potential wear on the gears. Is the spigot on the end of the 3rd motion shaft ok with no pitting. its important the needle rollers have a clean surface so they don't pick up. Unless there is wear on the shaft you can't really test for movement. Even assembled the train has a degree of movement anyway. |
| Bob Beaumont |
| Colin Can you post a close-up of the spigot on the 3rd motion shaft. If it's pitted, as Bob says, a needle roller bearing will dig into it. Mine was pitted so we made a phosphor bronze bush for it, as was used on smoothcase boxes, which will be gentler although won't last as long. OK so far. To check lateral movement of the needle roller, place it in the 1st motion shaft then insert the 3rd motion spigot and feel for movement as Jan says - there's bound to be a little. That bearing has a hard time. |
| Bill Bretherton |
| Maybe this is an early box using a bush rather than needles And the bush has worn away? |
| GuyW |
| If its a Midget box (88g229 input shaft) then it should be a needle roller. I think even the Minor ribcase has a needle roller. Perhaps the smoothcases are different. |
| Bob Beaumont |
| Jan, I knew I wouldn't get an accurate measurement, but I felt it would give an idea of the amount of play there is.
Bill, Bob, the photo of the spigot shows a small amount of pitting but I wouldn't have thought it was enough to cause a problem. The needle bearing has a small amount of lateral movement on the spigot. The second photo is not very scientific but it does give an idea of the slop between the two shafts. The third motion shaft is as close to level as I could get it. The input shaft is marked 22G229 which I understood to be correct for the 1275 Spridget but I have also been wondering whether it should have a bush instead of the bearing. I'm now inclined to go with Bill's idea and have a phosphor bronze bush made anyway. It might not last as long as a needle bearing but it should outlast me! Colin   |
| C Mee |
| Sorry I meant 22g 229! The movement of the shafts looks about right. There is always movement of the ist motion shaft anyway to allow it to mate with the engine! The other important bearing is the spigot in the crankshaft as this helps to hold the whole train in line. The pitting is not that serious. I would polish it up with some fine emery. so the rollers don't pick up. |
| Bob Beaumont |
| Colin
That spigot looks OK to me, better than mine was. I bought a PB bush that was close and used a friend's lathe to make it a good sliding fit. I drilled some oil holes in it (radially). Hopefully, it gets enough oil and will outlast me! But I presume they changed to a needle roller bearing for longevity (as long as the oil level doesn't fall). I may have made the wrong decision but it seemed to make sense in my case as excess pitting presumably wears through the case hardening. Are the dog teeth on the gears good? There was a good discussion about this a while back. |
| Bill Bretherton |
| Some people proceed in leaps and bounds, but not me, I think snails move more quickly than the work on my gearbox. I thought retirement would give me loads of time to work on my Sprite but I just seem to get busier engaged in 'stuff' that needs doing but which won't do itself.
Just removing the first motion shaft nut has taken ages as I had to go out and buy a spanner to fit the 1 38" AF nut. Even then I had to make do with an affordable adjustable as pukka spanners all seemed to be in the £50+ region which is a bit much for only two nuts, especially when the other one came off easily. Despite numerous applications of heat and persuasion with a hammer, it still wouldn't shift. I finally removed it yesterday courtesy of a 1.5mm drill and a bit of grinding with my Dremel, but not before I had received a couple of new replacement nuts before doing anything so drastic, hence a few more days' delay. Now, of course, I can't shift the bearing. I bought a bearing splitter especially for this job but, despite applying a combination of heat and gradually increased pressure over time, this has now stripped a thread! I've applied heat as precisely as I can to the inner ring of the bearing but don't want to over-do it and risk affecting the gear teeth. After heating it I've been using a brass drift against the bearing's outer ring but I'm reluctant to hit hard for fear of damaging the gear teeth. Does anyone have any other suggestions for removing the bearing or should I just bring out the Dremel again and grind it off? The only other alternative I can think of is to admit defeat and take it to a machine shop. Colin |
| C Mee |
| Hmm--
In the end of the input shaft there appears from here to be the remains of a roller bearing case, that will have to come out to get a measurement of the dia. to aid in selecting the correct bearing for the job Your output shaft spigot is stuffed, if you're going to run rollers on that you need to either replace it or take it to a machine shop and get it fixed --or if it's a desperate budget job stuff a bush in it . The bearing on the input shaft shouldn't be all that tight, normally you'd poke the scissors under it and press on the end of the shaft, they're usually that loose they don't even make the needle on the pressure gauge movIf you haven't got a press grab the out bearing in the vice and tap the end of the shaft with a soft hammer and it'll pop off ok. willy |
| William Revit |
| Colin Any of these 1 & 3/8 inch secondhand/NOS spanners any use?: https://www.ebay.co.uk/itm/295350251402?hash=item44c43f2f8a:g:OoEAAOSwAKljQXFO (not sure if these Jacobs Collet wrenches are thick enough for your use, as well as if they are of the correct opening - if so this and other ones are in £3-5 range on bay of the e. Or a £30 NOS Britool spanner: https://www.ebay.co.uk/itm/374357746542?hash=item572975e36e:g:zhsAAOSwNipjdLkC Cheers Mike |
| M Wood |
| If you don't have a large spanner you can grip the nut in a vice and use a large adjustable on the splines. Better still if you are scrapping the clutch friction plate push this on the spline and grip the centre boss with Stilsons.
I removed the front bearing by gripping the outer race in a vice knocking the shaft out using the wire wheel hammer. I think a worn flywheel spigot bearing was a major contributer to the noise. Heathrow didn't have any in stock but I managed to get one from Bearing Boys. I removed the old one using a rawlbolt and a socket as a spacer. Jan T |
| J Targosz |
| Thanks Mike and Jan.
I'll keep an eye on the Britool spanner on ebay Mike. I've removed the nut by cutting it off but I'm still going to need be able to do the new one up tight so I'll try the clutch plate idea first seeing as I think I still have the pre-engine re-build clutch lying around, sorry, safely stored away, somewhere. I'll give your method of removing the bearing a go tomorrow Jan. I'm still very uncertain about the sloppy fit of the needle roller bearing supplied by Heathrow so I think I'll pay BML Hayley AKA Bearing Man a visit. Thanks Colin |
| C Mee |
| What are the dimensions of the needle roller in the rear of the input shaft, I've not managed to find any details. I was wondering as inner rings for needle roller races are available separately and it may be possible to machine down the front of the 3rd motion shaft and fit an inner ring to it to get a new surface. |
| David Billington |
| Colin
Some other options for a spanner (searching: 1-3 8 Spanner), some good secondhand ones: https://www.ebay.co.uk/itm/134336504410?hash=item1f4714625a:g:FJMAAOSw1ypjMcro&amdata=enc%3AAQAHAAAAoKrXjqzFuH93fqYPZ6KSWmEpKzcGa5THTVQjh8rrs0e8ubL0WoJLLcux14WArEp6BCy5bo0GMHeXVvtS5F4HDlnfZKs0pk%2F6ekzqdDKbIFamKjBr9gsVbWd%2FdlixfUoAPQbw3dV%2BpS3ZJDEkVDbjgsQczRWfb79HgZPJSuWuK2sDc1Af1MRgYz9xrfpJv9ypp0wixgWUFjnZWJpas%2Bpmn9k%3D%7Ctkp%3ABk9SR_KIx4qWYQ Or https://www.ebay.co.uk/itm/204163251809?hash=item2f8913fe61:g:vRsAAOSwzGJivdAj&amdata=enc%3AAQAHAAAAoIvrE%2BoInVOA2ghBIyOOlcuGCTVKxvTIl4hXIQjyNP5MHKw5d7rGy8etRJbWPQt1KZH%2Bw8rUAQwjlwsf3lPESubWwlccJyNTgz4lZP%2BqLDh97reWY%2BMJvuGt5vftWqd5JHjJuHfyiPKQxHE3VhGPRvuhUp4ykwsVWfIqiWhEYBu0ehdaE%2BgolLvm2MP1TaVug%2BKgAPyzW75Pt7B9%2FNsRohE%3D%7Ctkp%3ABk9SR86xnYqWYQ Or https://www.ebay.co.uk/itm/233892919267?hash=item36751ab7e3:g:CzkAAOSwu51gJabN&amdata=enc%3AAQAHAAAA4BYq%2BEyfuUboimc0NqL8GJcIyi3YWazubYHKtpi%2FZL7vjddimcajk7HomnLVlOCli9N0Pc%2F0wIUVcYCAclW8J3BXf6YtZQrJgsouiFkUjgbMd%2FoLqZ97ErYtqlqBFO3BtWjf%2B%2B3VGMENEseVlojlfbnwOzoOMt08exOy9vUh7M91gjZ0pwfzoBwPcmEFYxdbNFm5LU2ZfBR50HzfnUo5srJk1OHs9jLH9aCQrO4iIgr%2B1uOA50%2FtV7WjbVLzT9hforOYaclmdMkWHpUGNTlSHbV8RBgoq2nFuUIqmz3WKu4p%7Ctkp%3ABk9SR_CIx4qWYQ Or https://www.ebay.co.uk/itm/284415869281?hash=item423881c161:g:mJwAAOSwsyNhHhg6&amdata=enc%3AAQAHAAAAoPeTz8dkeSecKTK44xmSoclgllk8BlMOKYDlZOWgFTT4e5wCln62yXjrLQNzLtTs24tbcPr%2FTudv6CfJub8zzjeHyTNmAxjI0swtlqi3UaJ25OGMQDYosVd03uCzy07awAz1maKDHRaH%2BhUFDUHaqGTXa8vTK4Zl1K%2F%2FwEKwK8zI1qzjqBE%2BGwzofhcdG994yUbpLU1Mkw33st%2FYOOEEPrE%3D%7Ctkp%3ABk9SR_aIx4qWYQ Guess you want open ended (inc a combination), so a ring spanner no use? https://www.ebay.co.uk/itm/266000239052?hash=item3deed989cc:g:apsAAOSwSwRjem~-&amdata=enc%3AAQAHAAAAoHQFdhFAUlECDR0Vp5Mc5Dz7SKX64Ja3eKRP3WetMUP8B9gVX2vOWD3ge%2F5NJVX2fz2BjvOt9wdkkNfWApKV0n2AM20aSmKkX%2F4LFLVcLl1Eitsp2gSQO42HCk6gyhRa3wo7I1tToY6hEFi57k488zJYhhKxX5TKSgcLEDqwiryyBgnj7RrBL0XaI3adsbsiGh%2BR7G2VlLpBZyaqjh5M6EY%3D%7Ctkp%3ABk9SR8bLuoqWYQ Cheers Mike |
| M Wood |
| Mike, you could save some screen space with those eBay item links by ending them at the end of the item (itm) number, before the question mark and all that follows it. Example - https://www.ebay.co.uk/itm/134336504410 Some Dave O'Neill taught me. |
| Nigel Atkins |
| Mike, Thanks for doing all that legwork. My feeble efforts had only turned up spanners at silly prices. The ring spanner looks ideal and should be on its way to me shortly. Thanks, Colin |
| C Mee |
| Colin As said earlier I fitted a PB Bush between 1st and 3rd motion shafts as my spigot was pitted like yours. 3rd motion shafts are almost unobtainium and expensive if you can find one. I looked into re-tipping the spigot but gave up on that idea. Maybe some boxes are run low on oil which would likely cause the spigot pitting presumably. |
| Bill Bretherton |
| Colin Happy to help and now I know how to search for particular spanner sizes. Hope the gearbox rebuild goes OK and keep us updated please on progress, no matter how long it takes. Nigel and Dave O’ - top tip on eBay links, will remember in future. I do like the friendly, helpful and informative BBS (I joined FriendFace recently to get some info on MkII Sprites - not the same). Cheers Mike |
| M Wood |
| Bill, What ways did you investigate for re-tipping the 3rd motion shaft. |
| David Billington |
| David I think over the years there have been a number of ideas tried. Building up with weld and then grinding back Cutting off the spigot and welding a new one back on (dubious!) Bill's idea although not the original bearing should work especially if you don't work it hard in the intermediate gears Denis Welch motorsport supply new shafts but not cheap!! at £395 plus VAT https://www.bighealey.co.uk/sprite-midget-parts/spridget-gearbox-4 |
| Bob Beaumont |
| I did some more searching and the needle roller bearing seems to be CHM172 which is detailed here http://www.butlerautomart.co.nz/our-range/Clutch-transmission/Bearings-bushes/Product-Specification-CHM172.aspx . The OD is odd so I think it's actually a 14mm ID x 18mm OD x 17mm wide which is readily available. I wondered about machining the 3rd motion shaft spigot down to 10mm and fitting a 14mm OD x 10mm ID inner race, they're available in various lengths and the next size I found would be 20mm long which could then be cut down.
|
| David Billington |
| David I can't remember the detail now but it was probably on the lines of what Bob said and may have included metal spraying which sounds expensive and none of it appealed to me. If you grind/turn down the spigot then aren't you going through the case hardening? In which case, surely it will wear quickly? |
| Bill Bretherton |
| Bill, Yes if case hardened it would go through the case but the idea was to add a new inner ring in its place to bring the spigot back to 14mm with a suitable hardened surface. A choice here https://www.bearingboys.co.uk/?catid=3665&display=&orderby=&att1=&att2=14mm&att3=&att4=&att5= . |
| David Billington |
| Bob Denis Welch also does refurbished lay gears for big Healey’s replacing the first straight cut gear - must work with all that power ! The chap that rebuilt my gearbox told me about it but reckoned it was not cost effective for our cars. |
| richard b |
| David Oh I see what you mean now! Perhaps that's the best solution. |
| Bill Bretherton |
| Machining the spigot on the output shaft and fitting a hard sleeve is the only/best option if you're going to run a needle race direct on it-and can't find a better shaft. It's a quite common procedure, any decent machine shop with a toolpost grinder can do it- Lots of Japanese boxes,Mazda,Ford, especially light truck gearboxes have replaceable wearing surfaces from new and if they wear it's a simple press off-press on job. |
| William Revit |
| Willy/ David Definitely the best solution then. If my box fails I'll aim to have that done. Is the sleeve an interference fit I.e. I presume there's no chance of it "letting go"? |
| Bill Bretherton |
| Hmm, this job just keeps getting more complicated. I thought it was going to be a 'simple' strip down and re-build. In my case, the supplied needle roller bearing has slight play on the 3rd motion shaft. There is more play in the input shaft. Could that be sleeved or is it possible to get needle roller bearings with larger rollers to take up the slack? How much play in either is acceptable? C |
| C Mee |
| Bill,
I would expect it to be an interference fit. The details of the dimensions the spigot would need to be machined/ground to should be available from the maker. Colin, You won't get a good idea of the fit with just the needle race in the input shaft or on the spigot as the needle rollers can move about a bit in the cage, the 2 need to be assembled together as you've shown earlier to gauge the play. With the wear on the spigot it really looks like that needs to be addressed properly. Have you asked Heathrow Transmissions if it's a service they provide. |
| David Billington |
| Found the full details here for the entire range https://www.ikont.eu/files/Documents/Catalogues/CAT-1573E_IKO_Bearings.pdf , page of interest is A42 table 22 which indicates a k5 tolerance or 10mm +1um to +7um. |
| David Billington |
| David’s comments about using replacement bearing surfaces got me thinking ! When I had my gearbox refurbed the lay gear was in good condition but the guy pointed out the inner surfaces where the needle bearings run was not good enough and a new lay gear was put in. If the cost of laygears / supply gets difficult it could be an option to add bearing rings - would need to grind out and push in. Shame I don’t have a tool post grinder (probably need a bigger lathe !) R. |
| richard b |
| David / Richard It's got me thinking too! Ideally I'd have sleeved the 3rd motion spigot. There wasn't much information about the spigot problem then but I'd guessed it must have been fairly common especially with gearboxes that leaked oil (all of them?). There's a decent machine shop near me so I might ask them for an estimate so we'll know if it's cost effective. |
| Bill Bretherton |
| Richard,
Have a look here https://www.skf.com/binaries/pub12/Images/0901d196803e7d9e-Catalogue---Needle-roller-bearings-06003-EN_tcm_12-271146.pdf in the section starting at page 97 for needle roller bearings with machined rings and see what matches the required size. Seems inner rings can be bought separately but not outer rings, they seem to come with the needle roller race but if the layshaft is good the needle roller should be good to run on that but it could be recovered with an inner race to suit. Maybe post the layshaft OD, laygear cluster ID, and bearing width so others can have a look as well for suitable bearings. |
| David Billington |
| Confessions of a clumsy mechanic.
The front bearing yielded to Jan's delicate approach - a big copper-headed hammer. Today, in amongst other jobs that needed doing, mainly cutting logs, I managed to take a look at the rear bearing. With the shaft mounted vertically in the vice and tapping lightly compared with the rear bearing and using a brass drift, the bearing and its housing moved relatively easily, though imperceptibly at first. All seemed to be going well until something pinged off the workshop wall! I hadn't realised how much the bearing had moved and the first gear assembly was following it down the shaft. Fortunately only one of the ball bearings escaped. I spent the next hour and a half emptying my box of wood off-cuts, tool boxes, shelves and other spaces where it might have hidden. I eventually found it hiding underneath a table, way at the back, after I'd removed all the junk/things that might come in useful stored there. Unless SWMBO has other plans, I'll trot along to my local garage and pay Bearing Man a visit to seek their advice and see if they can provide a solution. I'm beginning to think that Bill's solution of a phosphor-bronze bearing turned to fit is the way to go. C |
| C Mee |
| Colin Have you got all the springs?? I have got the special tool to re-assemble the first gear but you can do it using a wide cable tie to hold the balls in place before sliding the outer gear ring over. |
| Bob Beaumont |
| Yes Bob, all the springs and balls now safely in a labelled 35mm film container. I also added some spare ball bearings to my last parts order so I have a few spares 'just in case'. I've read about the Zip-tie method and have a stock - plus I have a have a large plastic tub to do it in and catch any errant balls and springs should they try to escape. |
| C Mee |
| Colin
That 1st gear installation is "fun". I think I used three small flat blade screwdrivers tied on with electrical wire and did it in an old washing up bowl something like you have. Make sure to align the gear correctly on the sleeve - it's possible to get this wrong and the box won't then select (I think) 2nd gear. Also, if you're doing hillclimbs (you mention in other thread) you need a good gearbox so maybe it's worth pricing up sleeving the 3rd motion shaft spigot. If uneconomic then go with the PB bush, like me, but I don't race or do trackday stuff etc. |
| Bill Bretherton |
| I usually dismantle the first gear assembly, and the 3-4 synchro, inside a plastic bag, in order to avoid escapees. Yes, it is possible to assembly the first gear assembly incorrectly. Haynes does cover this, although not particularly clearly, as I managed to get it wrong the first time I did it. I had intended to make a reassembly tool, similar to the BMC item, using some suitably sized plastic tubing, but have yet to get around to it. |
| Dave O'Neill 2 |
| Dave, as I'm often a belt and braces type, I think I'll try your poly bag idea inside my plastic tub!
Apart from letting one ball escape and then removing the rest of the balls and springs as a precaution I haven't dismantled the 1st gear assembly any further and it is zip-tied together including one holding the plunger in place all in a labelled poly bag. I paid a gearbox specialist in town a visit today. Before I reached the counter he said 'MG Midget' on seeing the main shaft so I'm confident that he's familiar with them. He took a close look at the spigot and passed it as acceptable with a bit of polishing with fine emery. He also approved the fit of the needle roller bearing on/in both shafts. I haven't touched the 2nd and 3rd gear assemblies and he advised that I should leave them alone. There is some wear on the 2nd gear dog teeth but not enough to justify replacement. This may be counter to the belt and braces approach, but it's one heck of a lot cheaper! So I think, after a bit more cleaning, re-assembly can begin when my big spanner arrives. |
| C Mee |
| Colin Your gearbox specialist sounds like would be a good person for a sensible rebuild if you and your budget go that way. Cheers Mike |
| M Wood |
| Mike, yes, I agree, I forgot to ask him what he would have charged. I only discovered him the other day. Quite a small operation but they have two places, one in Shrewsbury and the other in Telford.
On the other hand, a large part of the fun(!) of having the Sprite is the workshop side of things. I'm far from an accomplished mechanic/engineer but I've learnt a lot from working on it and grown in confidence which is why see tackling things like the gearbox re-build as another challenge to be conquered. When this one's up and running I'll have a better idea of how to tackle the leaky Minor gearbox that's in the Sprite at the present so I have a spare for my Traveller. My last job before retirement was editorial work on workshop and operation manuals for military vehicles. I picked up a lot from the engineers who were only too keen to explain things. Proof reading maintenance manuals on things that are far more complicated than a Sprite left me thinking 'I could do that' and now I'm actually having a go. If I were still at work I'd be picking my colleagues' brains on the issues I've encountered on this job so I'm immensely grateful for all the help and advice provided by everyone who has posted on this thread. C |
| C Mee |
| Hi Mike, I had the Ford gearbox that I fitted to my TF rebuilt by Jack Coultard in Paisley. This was about 7 years ago when the Type 9 'boxes could be picked up for fity pounds. He had a repair kit "left over" from the 1980s and never thought he would ever use it. The rebuild cost one hundred pounds. How things have changed. Cheers Jan |
| J Targosz |
| Colin
Do check the end play on the laygear and change washer if outside spec. Also, I'm no expert but I remember reading that it's good to change baulk (synchro) rings, especially if the synchromesh was "slow". I believe there is a case for keeping all the gears if they are "OK" as meshing new with old gears can make the box noisy, apart from the straight cut 1st gear which tends to wear and is noisy anyway. I changed the laygear (good price), 1st gear (the outer part) and the reverse idler plus the layshaft, synchro rings and bearings. It's reasonably quiet in 2nd and 3rd with 4th being quiet anyway as it's "direct". But your gearbox guy will know far more than I so I guess his advice should be good. |
| Bill Bretherton |
| Thanks Bill. I checked the laygear endplay before removing it and have a thicker thrust washer ready to go in.
One of the 3rd/4th gear baulk rings was well worn such that it almost bottomed out on it's taper. I'm replacing all three baulk rings which came in the Heathrow kit along with a layshaft, needle roller bearings and main bearings. I didn't know the state of the baulk rings before dismantling but it seemed sensible to change them anyway as they are almost consumables. Good point about mixing new and old gears. They all look fine to me and, though he didn't see them all, the gearbox guy said the ones he saw are fine. |
| C Mee |
| Oh dear, over a month since my last post. I'm sure plenty of folk here would have done the whole re-build from start to finish in a day. Thanks to Christmas stuff getting in the way I finally managed to spend time in the garage and make a bit of progress today.
I'm regretting not writing this thread in the third person as the 'my friend' incidents keep clocking up. My Ebay supplied 1 3/8" spanner arrived weeks ago, whereupon I realised that the nut it actually 1 5/16". Checking back I'd mis-read a couple of measurements on a parts website. Fortunately the spanner's fit was good enough to tighten the gearbox nuts without damaging them and I now have a 1 3/8 / 1 1/2" ring spanner that's bound to come in useful some time. If getting the input bearing off was a hassle, fitting the new bearing was no better. Despite leaving the shaft in the freezer for three days and heating the bearing in a pan of boiling water, it stuck half on. A friend agreed to press the bearing home on his 12 tonne press but he tested positive for Covid on the allotted day so I resorted to very careful and lengthy drifting with a brass drift. The output bearing threatened to be awkward but, after a night in the freezer for the bearing and a spot of heat from a hot air gun on the housing, everything slipped into place easily. Reassembling the synchronisers took a while and, thanks largely to handling them in a big tub, only two balls escaped and I found one of them. Thank goodness for the spares bought in case. A cut-down baked bean tin with a hole and a couple of cable ties made a passable substitute for the official special tool, though the 3rd/4th gear synchroniser took several attempts before everything was where it needed to be. All being well I should be fitting parts back in the casing tomorrow. Colin  |
| C Mee |
| Good job on getting it done. A certain satisfaction now that the end is in sight. A little late but I've always found that a large jubilee clip holding the balls in place worked well. Fiddle them in place while sliding the clip on, tighten the clip to almost tight and then just slide the gear into place. |
| Martin |
| Making progress but currently trying to get reaming of the new output shaft bush sorted. Today's question? Can anybody tell me the thread size for the reversing light switch? My Sprite is a pre-reversing light model and I'm not intending to fit one so I need to blank the switch hole as the box came without a switch and none of the bolts in my collection (as in Anam's 'At last, but not quite' post) have the correct thread. Colin |
| C Mee |
| Just when I thought the end was in sight, this job has just thrown up another problem to add to the saga.
The output bush was clearly worn and the bronze lining flaking so replacement seemed the obvious thing to do. It was a swine to remove and the replacement needed pressing in and reaming. I got a replacement bush from MGOC Spares. When I picked it up from the machine shop today he said the job was done but... which is where I butted in and said 'You've gone through the copper haven't you!' which was something I'd read about on a Morris forum. I think that relieved his embarrassment a bit. He definitely hasn't over-bored it as the prop shaft is a very snug running fit. So now I'm in a bit of a quandary: Do I just run with it to see how it fares? The oil groove is there so it should be lubricated. What could go wrong? (prop shaft seizes?) Do I try a different supplier and risk a repeat? Do I have the machine shop guy turn a solid phosphor bronze bush from scratch? I began regretting removing the old one some time ago. Colin   |
| C Mee |
| I emailed MGOC Spares who took my request for their comments seriously and sent a very detailed reply after consulting their gearbox specialist and their supplier who reported no previous quality control issues. Had the steel exposure been patchy it could have been down to damage caused when extracting the bush but it was actually quite consistent around the circumference and length of the interior. MGOC offered me a replacement, which I accepted.
I also obtained a bush from East Sussex Minors and there were minor differences in the two bushes which I duly presented to my machine shop guy to choose between. A week later my gearbox has a nicely reamed output bush with no exposed steel so the end of reassembly is in sight. However, I now have another quandry. With the gearbox out of the car I had hoped to find why engaging 1st and reverse was such a problem. I had put it down to the clutch dragging, possibly due to a bent fork, but that's perfectly straight. There was no drag when everything was cold, it only started when things had warmed up after a couple of miles so I suspected the spigot bush. I had forgotten to change it when I did the engine re-build in 2020 but I didn't have the dragging problem then. With spigot bush removed, I can't see any obvious damage although it looks as though it has been shortened with a hacksaw by a previous owner. Initially, I couldn't find the bush that I bought previously, so bought another. The replacement bushes came from the same supplier but are different lengths. I now have three different bushes. The one in the middle is the one original. Which one should I use?   |
| C Mee |
| When I did mine, the bush went in just below the hole in which it fitted in the crank. I would measure the depth of the hole in the crank and use the most appropriate bush. It certainly should not be proud. I think the later roller bearing bushes are much smaller in length than the original solid bushes |
| Bob Beaumont |
| Thanks Bob, that makes sense. As an aside, I can't understand how ordering the same part number can produce bushes of different dimensions. My faith in that supplier has suffered a few dents lately. |
| C Mee |
| Don't forget to 'fill' it with oil before you poke him in there |
| William Revit |
| Willy, the three of them have been soaking together in a 35mm film container full of oil for about a week - is that long enough! PS and cross-reference another thread about hanging on to stuff, my father's collection of 35mm film containers have been invaluable for this job. They've been perfect for holding ball bearings and springs and things that might go astray, all labelled with Sharpie with their parts diagram reference number. C |
| C Mee |
| Colin Yes a week will be fine! |
| Bob Beaumont |
| The spigot bearing in the Sprite's engine was extremely sloppy and the front gear box bearing absolute toast. I don't know which had failed first. The new spigot bearing I purchased was very loose on the nose of the input shaft and I was unsure if this was to take up any squash as the bearing was tapped into the crank. In the end I bought an under/over sized oilite bush from Bearing Boys and machined it to fit. I would have suggested that anyone without a lathe get a machine shop to turn down a bush but it is difficult to measure the I.D. of the hole in the crank because of the counter bore. I had to trial fit mine. If anyone is having a crank regrind it would be worth getting the machine shop to fit a properly sized spigot bush at the same time. Just as an aside I removed the old bush with an expanding rawl bolt, the ones used to fix machine tools to a concrete floor.
JanT |
| J Targosz |
| Well, I think I'm finally there!
The engine and gearbox went in on Monday and yesterday all the connecting up got finished. I'm just back from a first brief run out up and down the road (sans bonnet) and nearly all seems to be in order. The only issue (so far) is a leaking hose connection on the heater matrix and there are no oily drips on the garage floor. The gear change is much stiffer, possibly partly due to the spring beneath the gear lever, the old one was broken and I fitted the closest one I could find in my tin of springs and it was longer and a bit stiffer. It seems quieter that the old box, probably down to new bearings instead of worn ones. I've only driven it a couple of miles on a straightish road, so time will tell but I'm definitely feeling quite pleased with myself, and relieved that everything seems to be OK. I've included a couple of Before and After photos but the real business is, of course, what has gone on inside. Having done the job once, I would be happy to have a go at another one but that will have to wait until various other projects are behind me. I need to find a use for all the spare shims and bits that I bought 'just in case...' Thank you for all the comments and advice. I struggled a bit with this job but would have struggled even more without your help. Thanks Colin   |
| C Mee |
| Congratulations. It's a good feeling when you get something like this done. Now all that's left is to drive it. |
| Martin |
| Congrats Colin. Nice feeling when you rebuild a gearbox yourself, save money, and it works peoperly again. 🙂 👍. JanT. Grease, a correct sized bolt/rod, and a gentle whack with a hammer removes spigot bushes/bearings. 😁. Time honoured method.  |
| anamnesis |
| Colin Well done, good to get it finished. I rebuilt mine a few years before the car was on the road and although it seemed ok on the bench, there's always that moment of doubt when you first drive off (it worked btw)! |
| Bill Bretherton |
| Excellent News, Congratulations Colin, the first one is always the hardest!! |
| Bob Beaumont |
| Hi Anam, The "Time Honoured Way" is fine if you can find a bar of the correct diameter, or perhaps have a lathe or most importantly the bush is still circular. Cheers Jan T |
| J Targosz |
| Jan I've done it with mangled bushes and bearings. Any near enough sized bolt or bit of rod will do. I've never possesed, let alone even used a lathe in my life. Lol.
There's always more than one way to skin a cat. I always like the easiest. Grease, an odd bolt, and an 'ammer, very easy. Very quick. And these things you'll surely find in anybody's garage, who has the tools and nouse, enough to have taken their own engine out, etc. But fine, if you just happen to have rawl bolts in yer garage, and don't have to go out and buy one, that's a goodun too. 😁. How are you on the use of Stilsons for the rear hub nuts, or the 'acorns' on steering racks? Lol |
| anamnesis |
| Yep, I agree with Anam. Grease and pretty well any bolt that reasonably fills the inside diameter of the bush works well. And I would add that its strangely satisfying to do, finding it so easily effective. Somewhat like removing and then fitting a new flywheel ring gear. For a first timer it seems scary as one imagines all sorts of problems. But then you bite the bullet and do it and the satisfaction when it works perfectly is just great! |
| GuyW |
| next time you do a spigot bush, try bread instead of grease--lot better, less mess and you can eat the leftovers --lol |
| William Revit |
| Whole wheat, pumpernickel or rye? |
| Martin |
| Colin Excellent result and in time for the start of the hillclimb season. Cheers Mike |
| M Wood |
| Bread. Brilliant Willy. I'd never of thought that. Not sure I'd want to taste it after, but at least it'll costs you less dough. 😉 |
| anamnesis |
This thread was discussed between 03/10/2022 and 03/03/2023
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