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MG MGA - laygear shaft

Gentlemen
Below is a pic of the laygear shaft from my MGA. You will notice the wear. However, I replaced this shaft and bearings only 2000 miles ago!! There doesn't seem to be any oil supply issues and I can only assume that the shaft is way too soft. So, now I have to fork out for a new shaft, but that's not the real concern. If these shafts are too soft and wear that much over such a short mileaga how can I be sure that another shaft is harder? Would I be better to try and source a good secondhand one or can anyone recommend a good supplier?
Cheers
Matthew


M S Randell

I'm sure that's too little mileage for that much wear. Much info can be found on Barney's site.

http://www.mgaguru.com/mgtech/gearbox/gt204.htm

Beyond those options, the 5-speed conversion is easy.

If you did the rebuild work yourself, putting in a 3-sync MGB box should be no trouble for you. It shouldn't be too difficult to come by one.

There may be some specific problem with the layshafts being too soft right now, but I don't have that info.
Dave McCann

Thanks Dave
yes, I did the work myself. I'm only stripping it again because I replaced the second gear syncro ring and not the third (thought it was ok, duh!). Now the entire car is stripped for rebuild so I thought i'd fix the box again. I will consider the 3 brg MGB box option. I have a 3 brg MGB engine in the car.
Cheers
Matthew
M S Randell

When you get a new shaft, run a file across the OD at one end (where bearings do not run). If the file cuts metal, see how far you can throw the shaft. Some years ago there was a rash of soft layshafts on the market. Could well happen again at any time.
Barney Gaylord

Hi Barney,
This is the first time I am writing on this bbs.As I explained to you before my layshaft slipped out whilst handling the gearbox without the oil seal plate. I have dismantled the gearbox under the supervision of Frans Camilleri who gives me a lot of support and must admit that although it is quite a job this gives us the opportunity to know more about the car mechanics. We found the laygear shaft to be in very good condition and have fitted it back in place. Whilst inspecting the gears on the mainshaft I noticed that there are some dents on the teeth of the first gear.Although there is nothing broken do you beleive this needs to be replaced. The gearbox used to work fine. I am addressing this mail to Barney since I have already been in touch with him however any comments from anyone are very much appreciated.
c vassallo

Hi barney,
I have dismantled the gearbox as a result of ny shaft on my laygear slipping out whilst handling the gearbox without the panel for the oil seal. I am presently doing this through the sterling support and help that I get form frans camilleri. The layshaft and bearing seemed ok but whilst inspecting the other parts for any visible damage I could notice some dents on a number of teeth on the first gear. There are no broken teeth and hence I would appreciate your comments on whether this would require to be replaced, This would be quite costly.
I am addressing this mail to you since I have already been in contact with you but I would appreciate any comments from anyone. Thanks and regards from Malta
c vassallo

Years ago I can remember replacing a set of eight valve rockers on an engine with a new set from a discount store at what I thought was a remarkably cheap price. About a month later I noticed a tappet noise and adjusted the offending rocker gap. Two weeks later the noise returned and the same rocker needed adjustment. After many months and many adjustments I removed the offending rocker and found a large depression in the face from the valve stem. On inspecting the other rockers they were all perfect.
I assumed then that in the manufacturing process the parts were case hardened or similar and this particular bad part had been accidentally left out of the hardening process.
I would have thought that a layshaft would have been made out of high carbon or similarly hard steel but maybe case hardening a softer steel is a cheaper process more suited to smaller,lower cost manufacturer, in which case quality control would have to be good to prevent the process being missed.

I used to have a tin of case hardening compound for diy hardening of parts. I never used it but I think you just heated the part to a red colour and dipped it into the compound,probably containing carbon, and reheated to allow the carbon to diffuse into the surface.
There are quite a lot of metal surface treatment outfits around and I would have thought if you were keen you could get them to test the hardness and if low they would heat treat the part for you. However, it would probably cost more than the part did in the first place.............Mike
m.j. moore

Thanks everyone.
I guess I'll just have another go. I think I'll fit an extra set of bearings as per Barney's site, might help spread the load.
Matthew
M S Randell

>I used to have a tin of case hardening compound for diy
>hardening of parts. I never used it but I think you
>just heated the part to a red colour and dipped it into
>the compound,probably containing carbon, and reheated
>to allow the carbon to diffuse into the surface.

Without knowing how the shaft was originally made, it's hard to say what the correct course of action might be, other than keep buying replacements until you get one that passes Barney's file test. I would avoid using a surface hardening treatment like that unless you can establish for certain that was how the shaft was supposed to be made in the first place. You are going to have a real hard time trying to apply the compound in any kind of evenly controlled fashion outside of a real manufacturing environment. And if the shaft was supposed to be through hardened, and you only harden the surface, once the hard outer layer wears, you will be back to premature failure, though it would probably last longer at least.
Del Rawlins

c vassallo, -- At the moment I can only find one picture of 1st gear in relatively good condition, See attachment (including worn 2nd gear synchro ring). In this picture you can see some chips on the chamfered ends of the teeth. This is quite common and is not detrimental to operation. In fact rounding off of the chamfered ends can make it a little slicker shifting into 1st gear (and reverse). On occasion when I had one with lots of chipping on the tooth ends I would use a hand grinder to smooth off the burrs and any sharp edges and put it back in service.

On another issue, the driving faces of the teeth must be very smooth and clean. Common failure mode here is spalling. This means that thin chips or flakes are removed leaving a noticeable rough divot in the driving face of a gear tooth. If you have this condition the gear should be replaced (and please send me a picture of it to post as example of a bad part).

If in doubt, see if you can get a good close up picture of your gear and post it for us to see.
Barney Gaylord

Oops, attachment here.


Barney Gaylord

Matthew-
The file test is OK in a pinch, but use a new fine file, and lean hard on it. A very thin layer of hard material can give apparently good results (especially with a dull file) but still fail miserably, as your shaft has. Better, get a machine shop to hardness test the new one - this is way too much work to have failures in such low mileage.
The shafts are originally through hardened, though they are harder at the surface than they are deep down.
You absolutely cannot harden a finished shaft, as they must be finish ground to size AFTER heat treating.

FRM
FR Millmore

hi Barney,

Thank you very much for your info. In fact from the picture you sent I can confidently say that my gears look in much better condition. I have had a couple of other opinions from other people who saw the gears physically yesterday and they are of the same opinion.
This afternoon we managed almost to completely assemble the gearbox with Frans Camilleri , but whilst pushing one of the selector rod we noticed a ball bearing jumped out but managed to retrieve it and put it back in place on the synchroniser. When I was handling the gearbox from the workbench Frans noticed two other balls had fallen down on the floor, obvoiusly there were three which shot out. This was very disappointing moreso when we thought that the job was almost complete. Before I start taking it apart again is there any possibility to rectify this situation without dismantling the gearbox completely . Looking at the bright side we were lucky that the balls fell out.
Your advices are always very much appreciated
Regards

charles
c vassallo

again, thanks to all
I've ordered a new shaft and I'll fit an extra set of bearings, probably the original 20 roller type. Problem of course is that I won't know if the new one has prematurely failed unless I strip the box periodically. . . hmm. . not likely really!
Matthew
M S Randell

Hi Mathew,
Have just come accross your posting. I fitted a new Moss shaft to a cuastomers 67 GT & it only lasted 1000 miles. I had it tested & it was only 57 'rockwell'. They need to be at least 62 so I had a batch made locally, used 1 in the cutomers car & kept 1 for my own 66 GT. Paul Walbran Motors
(ph 006498178194) bought the remainder but I think he has sold them all but now gets them made when needed. The same problem is with the 4 synro ones too.
I fit the mainshaft 8G2404 needles to the 1st gear end and shorten the spacer to suit. Did this on my GT years ago.
Garth
Garth Bagnall

As I said "Better, get a machine shop to hardness test the new one - this is way too much work to have failures in such low mileage."

So annoying that suppliers can't get even the basics correct!

FRM
FR Millmore

The trouble with all this is that people like Matthew,Garth and possibly many others have been involved in extra expense,heartache and time in getting around the problem and Moss, who are responsible, get off scott free. I'm worried now about the new one I put in my box a while ago.

Moss will continue to supply inferior parts because they are not losing out but I know it's difficult to return something that was bought a long time ago.

I think the only way to put pressure on Moss is to have a parts list published on the web with recommended suppliers against each part and/or points to watch out for.................mike
m.j. moore

Not that I know much about these shafts, but there is a video on Youtube from University motors (search for it), where they guy shows two similar looking shafts but with very different properties....He does the 'file test'.
Anyway, my 1cent worth.
G Ramos

ok so we had to dismantle completely the gearbox again . However my friend Frans camilleri came up with a brilliant idea whereby he fitted an o ring tightly around the roller bearing before placing the mainshft into position and then cut it and took it off. Also we used a jubilee clip to hold the ball bearings in place as we slipped the gear on the syncromesh
We are now satisfied that the gearbox is completely assembled again, this time with the two balls in place
c vassallo

Question for Matthew - who was the supplier of your "soft" layshaft?
Art Pearse

Hi Art
Not sure. I bought it through a local supplier; probably Moss, but I couldn't be certain. I have fitted the new layshaft with an extra set of bearings on the first gear end. It will be a while 'till I drive the car, so I hope all is ok.
Matthew
M S Randell

Actually, I should say that I used the caged bearings but I had kept the original sets. (never throw anything away). So I used an original for an extra set. So I have a mix of old and new.
Matthew
M S Randell

How difficult was it drilling the new oil hole? (You did, eh?)
Art Pearse

Art -
Extra oil hole is not really necessary, since these bearings only need minimal lubrication, and there's plenty in there. But, if you are familiar with drilling hard stuff, it will provide an excellent hardness test!

FRM
Fletcher R Millmore

Thanks Fletcher. I think I will forego the hole as you suggest I can, it will get the oil from the adjacent brg.
It is amazing the difference - no perceptible wear on the front 2, totally ruined on the rear.
Art Pearse

One reason for that wear pattern is that some people used 1/2 a lot, as in traffic driving, while road drivers used 3/4 much more. We used to see a lot of difference in the patterns on cars used differently, just like clutches. But the original design was clearly deficient, since it could be expected that some cars would get lots of 1/2 use, and most likely both ends of the laygear are going to turn the same number of turns - except the last one. Had a few where the front end turned one more time than the back - ugly!

FRM
Fletcher R Millmore

Yes Art
Didn't drill a hole. Too difficult and I really think the bearings get plenty of lube. The lay shaft is half in oil anyway.
Matthew
M S Randell

This thread was discussed between 07/02/2010 and 14/03/2010

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