MG-Cars.com
MG MGB Technical MGB Overdrive BBS discussion at MG-Cars.net
MG-Cars.net
Welcome to our resource for MG Car Information.
Recommendations
Parts
MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.
|
|
MG MGB Technical - MGB Overdrive
| The OD on my 74 B engages intermittently. Driving the car the OD will work correctly, 10 miles later it won't work at all. The next time I drive the car it's the same problem. The car has been recently serviced so the gearbox oil level is correct although I dont know what the grade of oil is. Am I looking for an electrical fault?? Thanks. |
| John Cotgreave |
| Common faults are the dash switch and the inhibitor switch.
If it is the dash switch, then switching it 2 or 3 times more or wiggling the toggle side to side can produce a result. (though not always) If the inhibitor switch, holding the gear lever hard to the right while still in top or 3rd can encourage it to make better contact. But again, not always. If the simple tests don't show anything, attach a test light to the bullet connector just before the solenoid, with enough wire to have the light within sight of you |
| Paul Walbran |
| “The car has been recently serviced so the gearbox oil level is correct...” Have you actually checked it? I filled my gearbox before refitting it to the car, as I figured it was the easiest way. However, after driving it, the oil level dropped considerably. My overdrive still doesn’t work though, even with the correct oil level. I haven’t had time to investigate it yet., although I have eliminated the electrics. |
| Dave O'Neill 2 |
| The easiest way to check the electrics on a 4-synch MGB with the dash switch is to connect an ammeter in series with the manual switch. Testing the bullet by the solenoid is not only tricky to get to, especially to monitor it while driving, but only checks voltage is reaching that far, it doesn't check the continuity to earth via the solenoid which current does. Later models with column and gear-lever switches can be checked by interrupting the appropriate wire where the gearbox harness joins the main harness in the engine bay.
You should see about an amp, and if you see that when OD won't engage then it isn't an electrical problem. It could still be a solenoid problem - binding, or pump, or relief valve. The solenoid and relief valve can be removed and cleaned/checked without draining the oil, but that's about it apart from connecting a high-pressure gauge. After that it's a case of draining it to check the pump, and after that taking it out and sending it away. |
| paulh4 |
| John,
(in addition to Paul's info) on this site somewhere is a page of John Twist explaining the common faults, sorry I can't find it now but a search of the internet may bring you to it or on John Twist's site or elsewhere. Also there are three John Twist videos on repairing the o/d (and others on how it works) which may help you, certainly the first of the three. You have to go back a bit to find them (104, 105, 106(?)) - https://www.youtube.com/user/Universitymotorsltd/videos Obviously I have no idea with whoever recently serviced your car but to many a full service is changing the engine oil and filter, if you look in your Driver's Handbook you'll see there's a little more to it for even a 6 month/6k-mile service let alone 12/24/30/36. If you don't own a copy of the relevant Driver's Handbook yet you'd be very wise to get one, example of my midget one below (it's not a workshop manual but for the driver/owner). The (engine) oil in the gearbox should be changed every 24 months or 24k-miles, most cars its changed very rarely/decades/never. Whilst changing the o/d filter is also cleaned. Some places are magically able to tell the oil level without lifting the dipstick or knowing its location or existence.  |
| Nigel Atkins |
| Sounds to me to be more likely a bad seating on the OD pump non return valve or the solenoid ball valve- giving you low oil pressure once the oil in the box has warmed up. Both can be accessed under the car after draining the gearbox and removing the solenoid retaining plate and the filter plate. |
| Chris at Octarine Services |
| Good point Chris, sorry I did not read John's post properly. We have on more than one occasion found the ball in the the solenoid valve to be missing altogether and giving this result.
I usually prefer a meter to track electrical issues, but in this car the value of a test light is that it's easier to observe when driving. For an intermittent fault it is invaluable to have the light easily indicating while road testing whether or not voltage is reaching the solenoid, then any correlation or not between that and the intermittent operation can be easily established. If there is no correlation then hydraulics or possibly solenoid coil are implicated. Our full road test rig also includes a pressure gauge with enough hose to attach the dial just inside the 1/4 light, and this shows up any hydraulic issues - some of which become evident only during a long drive. |
| Paul Walbran |
| A test-light would need to pass sufficient current to ensure reliable operation of the solenoid, which is why I use a meter. I have to say I prefer analogue meters in any event, but in this case it only needs a glance and doesn't have to be 'read' a a digital would. |
| paulh4 |
| Hi Paul
We set the light up in parallel rather than series so it simply establishes whether or not voltage is reaching the solenoid without interfering with the current. Certainly it doesn't confirm the current in the solenoid is correct, but solenoids are seldom intermittent and if the fault is intermittent then the easily detected on/off simplicity of a light is worth it. Used in conjunction with the pressure gauge, if the light shows that voltage is present, then the pressure gauge reading (nil, very low, marginally low etc) and how it changes after a few miles as things warm up gives us a very positive steer. |
| Paul Walbran |
Paul - as mentioned earlier that still only proves voltage to where your test-light is connected, not all the way to and through the solenoid. I have had a problem at the solenoid where the 'ears' at one end should make contact with the casing for the earth. They had gone flat over the decades and weren't giving a good connection. Each to their own.
 |
| paulh4 |
| Continuing my B overdrive woes, I have had an auto electrician check the electrical operation of the OD, didn't find any problems. He wired an indicator led to the dash, OD engaged, the light is on. Now appears to be a mechanical problem, but I'm thinking....thd OD will work from a cold start for 15 - 2o kms, then will not engage. Warm gearbox/od oil if it's the wrong viscosity causing the problem? |
| John Cotgreave |
| John, have you yourself checked the oil level in the gearbox? Do you know when the oil was last changed, how many months, years, decades ago? Did you have a look at those John Twist videos on cleaning the filter and further work and repairs. What's the weather like? |
| Nigel Atkins |
| It took a boit of out-source finding but here's the MGB o/d from JT - https://www.mg-cars.org.uk/news/news363.html |
| Nigel Atkins |
| John,
I got my usual garage to change my gearbox oil last year & i watched the mechanic refill the gearbox with a huge shringe & flexible pipe (20 /50 classic oil) until the oil gushed out. (At the time both filters were changed). On the way home (a relatively short trip the O/D cut in & out when operated ,although i thought it wasn't quite as quick as before i took the car in). A drive later that day showed that the O/D sometimes wouldn't kick in at all for a few moments. Knowing that i would be checking the level of oil again in a few days at home i put up with it. After those few days i got the car up on axle stands & perfectly level (with a spirit level) i was able to top up the gear box with maybe 3/4 + a pint of oil. Following that the O/D has worked perfectly with no hesitation. I would check the level first before assuming anything more serious. See attached extract from the handbook (last sentence in particular). Cheers,Charles  |
| Charles9 |
| You do need to cycle the OD on and off a couple of times and I put it through the gears as well, before re-checking levels. Not wanting to drive either of mine with a low level I chocked the front and raised one rear wheel just enough to clear the ground, before lowering it again and rechecking.
But I doubt that's the issue here, as with a marginal level it will drift in and out of OD, other than that it will either work or it won't. Nor viscosity unless he put something really odd in. Even if your auto-electrician checked the current as I recommend, because it's intermittent unless you monitor the current while driving you won't know whether that changes when OD fails to engage i.e. it's electrical, or whether the current is still correct i.e. the problem is mechanical or hydraulic. Other than that the only other valid test is a pressure gauge, but that still needs to be connected when the OD stops working after a few 'miles' to be any use. |
| paulh4 |
| John - read my comment above - it answers your last question. |
| Chris at Octarine Services |
| It probably won't be the oil level but an assumption has been made that the oil level is correct it is very easy to check and this should be done before moving on to more sexy technical diagnostics.
There's nothing to say the g/box oil was actually checked let alone a service including changing the gearbox oil and checking the filter. If the oil hasn't been changed and filter check for a while then it would want doing soon anyway. To save our necks, the extract of the good book Charles has put up. ETA: Chris, I think (can't remember) the JT vids cover that too.  |
| Nigel Atkins |
| My story, if I may?
I bought my 73 roadster about 27 years ago. For the last 10 years it has been a cupboard, rather than a car. That is, until last month. Now it is definitely a car and has cover nearly 250 miles in April. I'm getting there with most of the mechanical bits and pieces and have spent many hours browsing old forums and learning what everybody else seemed to know many years ago. I'm now chasing a fault(s) on the overdrive. It should work in 3rd and 4th, and I remember it used to. Now it doesn't work at all. First up as a part of getting back on the road I changed the gearbox oil, but couldn't remove the o/d sump. The oil is filled to the right level. Next I've checked the voltage and current at the dash switch. I'm getting 12v, but only a temporary minor flick of the needle when I check for current. Just a few milliamps. Oh good, I thought, I've found a problem. So, I headed off into the engine bay, found the yellow to yellow/red bullet connector and cleaned it up. The live side is giving me 12v. But no, still no current. I've tried pulling the gear lever over to help make a better connection, but no. I've read about all sorts of shenanigans looking at the gearbox switch, the solenoid bullet connector and the solenoid earth. Any votes for which order I should do these in taking into account the ease to carry out the check and likelihood of finding a fault? |
| Gordo |
| Thanks all for your comments, I will work through them and keep you up to date. First thing to do is to check the gearbox oil level. Nigel Atkins.....we have had a week of lovely sunny weather here in NZ. Won't last though!! Cheers. |
| John Cotgreave |
| Update.....gearbox oil level checked. Not the easiest job to do but the previous owner had put a cable tie on the dipstick making it easier to get out. Oil level correct and the oil is clean. |
| John Cotgreave |
| Gordo - the next place to check would be the gearbox switch.
If you lower the removable cross-member under the gearbox that will give you more room. Then inside the car remove the gear lever knob, gearbox trim-ring, gaiter. Remove the screw at the back of the arm-rest cubby and pull that centre section back and off the gear lever. There should be a small removable panel on top of the tunnel round the lever, but the front section may be covered by carpet. If so cut the carpet forwards and round that panel (as in the attached), keeping it to refit later, it saves you having to pull the tunnel carpet back from under the centre console.. Remove the panel. Now you should be able to see the switch on the passenger side by peering forwards through the hole. You should be able to pull the gearbox to one side with the gear lever to give you a bit more apace, and to be able to get a meter probe on the two spades. With the ignition on, manual switch on, and the gear lever in 3rd or 4th, check both terminals of the switch for 12v - and indeed that the wires are connected! If you are going to leave the ignition on for any length of time disconnect the coil or it will overheat. Also listen for the fuel pump clicking, it shouldn't do so more than once every 30 secs, but even if it is less frequently than that the float valves could be seeping very slightly which will eventually cause an overflow so watch out for that as well. If there is 12v on both then it could be the bullet connector that is down the side of the gearbox, or it could be the solenoid. There is not enough slack in the wiring to pull the bullet connector up far enough to test both sides, or down - without taking the wiring off the switch which rather defeats the object for electrical testing, so my preferred option now is to check the solenoid. With the car safely supported remove the square plate with all the printed info on it and the solenoid can be withdrawn, so you can now check for voltage and current using the copper springs on the internal end of the solenoid and earth. Check those copper springs are bent out as per the image I posted earlier, the one on the right, and are not flat like the one on the left. More pictures here http://www.mgb-stuff.org.uk/gswitch.htm#2c  |
| paulh4 |
| John,
good that the oil is at level and looks clean, I'd still recommend if it hasn't been done in the last couple of years that at some point the gearbox oil has a thorough change (drain as warm as possible for as long as possible) and the filters cleaned, as per the page out of the Driver's Handbook. Even clean looking oil can be less so with crud or bits in it out of the lower drain plug position when you do a through drain and refill. Engine oil in the gearbox isn't as robust as gear oil and the factory Workshop Manual has gearbox (o/d) oil changes at 24k-miles or 24 months whichever is the sooner. |
| Nigel Atkins |
| Gordo, I'd recommend the same for you, I'd even say another oil change as part of it, taking the existing oil as being useful as a flushing oil. A thorough oil change (drain as warm as possible for as long as possible) and the filters cleaned, as per the page out of the Driver's Handbook. It'd probably pay to get the sump (and relief valve) filter clean too. |
| Nigel Atkins |
| Many thanks for taking the time to give such clear instructions. I've followed them fairly closely and have been able to remove both cables from the gearbox switch. I linked them with my ammeter and voltmeter and could see I still had 12v and minimal current. So, I refitted them.
I moved on to the bullet connector just before the solenoid. There was some spare cable looped up beside the gearbox switch, so I lowered it and was able to disconnect, clean, test and refit the connectors. That all seemed fine. 12v and minimal current. I did notice the wire from the bullet connector to the solenoid was in a poor state, and that could be the culprit. My next job will be to look at the solenoid earth. After that it's the GB oil change and filter. Thanks once again. |
| Gordo |
| OK, further comment on my B overdrive. I contacted the previous owner of the car and he told me that he had experienced a similar problem from time to time. It ddnt worry him as other B owners had told him they had the same OD problem. He was able to confirm that the gearbox/OD oil had been changed recently, the correct grade used in the box(20W50) and the OD filter was replaced. |
| John Cotgreave |
| "other B owners had told him they had the same OD problem" Definitely not right. Apart from the solenoid problem I described I've not had intermittent problems on the roadster in 30 years and 65k or the V8 in 24 years and 100k. |
| paulh4 |
| I concur with Paul. I've had my car from new 39 years ago (78k miles +) & other than the recent hiccup due to low oil , i have never experienced the intermittent problem you have. Cheers, Charles |
| Charles9 |
| I'm still building up my stock of spanners. I can see the plate with the writing on it needs a 5/16 spanner and I've got one of those. However, the 6 bolts securing the plate next to it are secured by 37H1946 bolts. Pl could somebody be kind enough to let me know what size spanner I need as none of mine are right? |
| Gordo |
| John, look at Chris's first post, I think that's pointing in the right direction. We have seen quite a few where the ball in the solenoid valve has been lost and it does just what you are experiencing. As does the oil pump non-return valve ball. |
| Paul Walbran |
| Don't forget the six are securing the pump and the oil needs - well, preferably anyway - to be drained before removing that, and some more will still come out. I have a 3/8" socket set that includes as many 1/4" drive sockets with adapter as 3/8" drive, and those fit the OD screws. I use that 3/8" ratchet more that I use my 1/2" set. From my reading John is experiencing intermittent non-operation. Lost balls will result in it not working at all. |
| paulh4 |
| Gordo, from an earlier post of mine have a look at the John Twist (University Motors) videos as I'm sure he mentions all the spanners sizes (5/16" actually BA IIRC). Also there are three John Twist videos on repairing the o/d (and others on how it works) . . . You have to go back a bit to find them (104, 105, 106(?)) - https://www.youtube.com/user/Universitymotorsltd/videos |
| Nigel Atkins |
| John,
"other B owners had told him they had the same OD problem" - it's the old "they all do that", what we technically refer as a load of old bollocks - they have the same problem probably for similar reasons but it's not because "they all do that". The o/d should engage and disengage almost immediately at the flick of a switch, and you do not lift (entirely at least) off the accelerator as the o/d works off the loading and you do not need to dip the clutch pedal. I would use my Bs as daily drivers and for work, commuting, holidays and tours and I'd expect the o/d to always operate as I put. The thing is a lot of classic car owners, even long term owners, have no idea how their vehicles could or show perform as they don't drive them enough or drive other mechanically good examples to compare against, so these owners accept the lower standards. They also don't know how to fully operate or look after their vehicle because they don't own or read the relevant Driver's Handbook. How to operate the o/d is of course in the Driver's Handbook along with lots of other drivers info. As well I'd suggest you try to find a local(-ish?) good mechanical example of a B (not necessarily great looking and shiny) to have a ride out in to see how well MGBs could and should go, a local MG club perhaps or B owner. |
| Nigel Atkins |
| John-
Disconnect the two wires from the Overdrive isolation switch (transmission lockout switch), and then attach your Ohmmeter to the two contacts on the Overdrive isolation switch (transmission lockout switch). The ignition switch does not need to be in its 'On' position. Your Ohmmeter should show close to 'Zero' resistance when the gear change lever (gearshift lever) is positioned in fourth gear, and Infinite (∞) resistance in all of the other gears. If you only have a reading of 12 Volts of electric current on one side, then the Overdrive isolation switch (transmission lockout switch) probably either needs resetting by means of shimming by means of fiber washers, or may be faulty. This switch is identical to the switch that is employed for the back-up lights, having same part number (BMC Part # 13H 2154, Moss Motors Part # 140-070) for the Three-synchro as well as the Four-synchro transmissions, so for comparison-testing purposes you can use it for a substitute. If the Overdrive isolation switch (transmission lockout switch) needs resetting, sometimes pulling the gear change lever (gearshift lever) to the right and to the rear while in 4th gear can operate the Overdrive isolation switch (transmission lockout switch). The Overdrive isolation switch (transmission lockout switch) was originally installed along with a couple of red fiber washers (BMC Part # 1B 3654, Moss Motors Part # 324-125), therefore investigate in order to establish that it is tight. If it is tight, then remove it, take out one of those fiber washers, and then test it again. |
| Stephen Strange |
| As I read Johns problem, it is consistent rather than intermittent. OK when oil cold, not as it starts to warm. If so, that is usually pressure bleeding away. And yes, I have seen that happen when the ball is not present. In addition to that and the pump non return valve, it can also be due to a weak solenoid and a wrongly shimmed relief valve. Theoretically failing o-ring on an operating piston would also cause this but I have been lucky enough to not find this to be an issue. Yet. |
| Paul Walbran |
| Resistance is not a good 'measure' of switch performance as the contacts are not gold and they oxidise. Normal current is enough to burn that off but ohmmeter current isn't. I remember someone who rebuilt gearboxes for a living saying he always tested the switches with an ohmmeter and ended up changing most of them, but how many fail in use?
The only true way to check the circuit is with current. Not even voltage is good enough unless the circuit is taking its design load, as again voltmeters only result in microamps through he switch, but in that case it can be concealing a bad switch. A voltmeter will show 12v even when there is resistance of hundreds of ohms back towards the supply. Gordy said he took the wires off the switch and linked them with his ammeter, so the switch wasn't even in circuit. He still got minimal current, so the switch isn't the problem. The difficulty is that in a car that hasn't run for 10 years there could be more than one fault. So strictly speaking one has to measure voltage at various points in the completed circuit, whilst at the same time measuring the current. If the voltmeter shows 12v on both side of the (for example) closed switch, whilst showing no current, then you can say the circuit back to the supply isn't open-circuit, but there IS an open-circuit or high-resistance fault further on towards (in this case) the solenoid. You could still have a high-resistance fault back towards the supply, but you won't see the effect of that the voltmeter until you have completed the circuit through the solenoid. At that point, if there is a high-resistance connection back towards the supply, then you will find you have lost the voltage down-stream of that fault, which can be really puzzling. It's why it's called 'electrickery'. |
| paulh4 |
| I forgot to point out with the link I put to the John Twist page on this site (see below) refers to USA cars but the basic principles remain the same.
Going slightly of current topic and referring only to the solenoid, and not modern made electrics either, - "Solenoids do not fail. The number of owners who purchase a new solenoid to correct their overdrive problems is unbelievable! I have encountered one faulty solenoid in 25 years! And that one I simply unwound, repaired the wiring, and rewound on the lathe." https://www.mg-cars.org.uk/news/news363.html |
| Nigel Atkins |
| Nigel, while I agree that looked unnecessarily buy a new solenoid on the majority of occasions, I have found them to be weak and therefore failed. We have a test right to measure the release load when pushing back onto the ball, and have found a small number over the years which have less grunt than they should have done.
Late at night and the figures are not in front of me, but from memory and quick maths to maintain the required 400-odd psi the ball needs to be held onto its seat with a force significantly in excess of 6 lb. (if only just 6lb then the ball is just on the cusp of bring pushed back off it's seat by the operation g oil pressure) |
| Paul Walbran |
| Paul Walbran, thanks for your comments I will continue to investigate the OD problem, you have been recommended to me as a source of spare parts for my B. Cheers and thanks again.JC. |
| John Cotgreave |
| Hi Paul,
on re-reading my post I see what you mean and I apologise to you. It wasn't my intention to dispute you, or others, I was as usual rushing and to be honest lazy by not just adding a quick sentence to say the solenoid might not be the first item to check or cause based on what John Twist has put in the article I referenced, which was what was in my mind - but I didn't write it, sorry. I wasn't trying to suggest you or the other Paul (or others) where barking up the wrong twig let alone tree, you both have more knowledge on all the B subjects in the nail of your little fingers than me, I was just putting up the basics and I think the JT vids (whilst not perfect) cover a lot of basic info. I'm also aware that there are far more readers than contributors to a thread and will be in the future if this thread is referenced and not all readers will have the specific issue so looking for more general information. This of course means sometimes my posts won't be bull's eye to issue but hopefully on target but I couldn't put this explanation on every post that it applies to, mainly as I'd forget. As I've put in an email only this morning, I know these problems can be caused by other pressure issues but I always like to check the basics first (because that’s all I know) especially with things like gearboxes and overdrives that can be time-consuming and costly if they need to come out and be repaired and because these types of components are very often overlooked for servicing and maintenance and often that’s all they need. {often, not always I know} How many B owners change the gear (engine) oil ever let alone every two years or clean the o/d filters or even check the oil level in the gearbox. I always expected the o/d {on my cars] to engage and disengage almost instantly without lifting my foot from the accelerator or dipping the clutch pedal yet other B owners think you have to do either or both and think 2 or 3 seconds or more is normal for engagement or disengagement and this belief spreads among other B owners and it becomes the norm “they all do that”. This post also proves spending just a little more time on what you're doing at that time can save time later. :) |
| Nigel Atkins |
| Same here, Nigel, regarding engagement and disengagement. If you disengage on the overrun with significant revs you do get a jolt, which is why the D-type had a solenoid and relay which prevented disengagement until you opened the throttle, or came out of an overdrive gear.
Other than that any sensation should be slight and nowhere near damaging to anything, and engagement shouldn't result in any at all - lumps and bumps in today's roads should gave more than that. The shims in the relief valve control the 'sharpness' of operation - adding shims softens it, removing shims sharpens it. |
| paulh4 |
| Nigel, no offence taken at all, I assure you. In fact I thought you made a very valid point, my comment was just to note that, while the solenoid often replaced unnecessarily as you noted, occasionally can be an issue. Paul, your last comment about shims: is it the right way round? Might be my brain isn't working yet being too early in the morning, but I think adding shims increases relief valve release pressure, and higher operating pressure gives a sharper engagement? |
| Paul Walbran |
| Thank you Paul, but as often happens I didn't put it well or what I really meant because I was rushing too much. I'm too long-winded for short posts usually. :) |
| Nigel Atkins |
| My mistake, should have looked in the book yet again but having done that and written it just a few days ago I thought I could remember it! Adding shims sharpens it, removing shims softens it. |
| paulh4 |
| I know that memory fail feeling well! |
| Paul Walbran |
| I was scratching my head lots on this. I know that 2 resistors in series would give a voltage drop between them. So I just couldn't understand why I had 12v and no current when tested at the solenoid. I bought a set of spanners and got it all apart. I changed the o rings whilst I was there. Eventually I doubted my AVO meter. It must be wrong. Well, the meter was correct. It was user error. I had 12v DC and absolutely no AC current. Doh! A flick of the dial and 800 mA appeared.
Oh, and thanks for the nudge about changing the oil in gearbox including the overdrive. I was amazed how mucky it was. However, still no OD, so I'm going to have another look at the solenoid and clean the piston. Then, if no joy I will do another oil change in a month or two. I'm not into pulling bits out of the unit in case I can't get them back in again. |
| Gordo |
| Easily done. You can power the solenoid on the bench, the piston isn't going to fly out, when magnetised it only moves to the middle of its travel as in the attached. Make sure the little ball is in the end-cap, you should be able to see it by looking through the holes on the side, as well as if you remove the end-cap - don't lose it.
You can remove and clean the valve assembly. There are variations in these as here http://www.mgb-stuff.org.uk/goc.htm#3 The plug for that is by the solenoid, but you may have to drain the oil first or risk getting parts washed out. Then the pump, which needs sump removal. A small spring and another ball just above the plug with the two holes. No experience of working on those, make sure the plunger with the wheel on the top goes in at the right angle to act against the cam. After that a pressure test is the only other thing you can do in-situ.  |
| paulh4 |
| Gordo,
as you'd already changed the oil recently even I was a bit surprised to hear it was very mucky, I should have put my usual about doing the oil change thoroughly. Have the oil warm/hot to drain, leave to drain as long as possible, overnight is good with the filters removes whilst you clean them. I'd also whilst the box is totally open at the bottom tip some warmed (can in the sun on concrete if warm day or in bowl of warm/hot water inside if not) fresh oil through the box and allow to fully drain as a bit of further flush. Refill with fresh oil, turn through and operate the gears and check level after oil has settled and check level again after first road run, top up if required and forget about it for another two years. Now, if you back axle oil is 10 years (or more) old then it's simple job to do a similar hot/warm drain, tip flush, refill on that too. |
| Nigel Atkins |
"Make sure the little ball is in the end-cap, you should be able to see it by looking through the holes on the side, as well as if you remove the end-cap - don't lose it. " When you remove the retaining cover plate and pull the solenoid assembly out, normally either the piston will fall, rapidly followed by the tiny ball, or the cap of the assembly will stay in the casing and the little ball again makes its bid for freedom - be warned! |
| Chris at Octarine Services |
This thread was discussed between 21/04/2019 and 04/05/2019
MG MGB Technical index
This thread is from the archive. The Live MG MGB Technical BBS is active now.