diff rebuild

[cadetchris]

having deduced the whine in Primrose has nothing to do with the prop shaft u/j's, the next logical thing is the diff.

so, how does one rebuild the thing?
what bits are required?

[bmcecosse]

Read the workshop manual - to do it properly you need gauges and much patience...... It's not something I would be tacking!

[kennatt]

nor me,specialist tools and a lot of expirence,and getting the pinion to crown wheel setting right is an art in itself or the whine will be a lot worse. Find a known good second hand unit or get a gear specialist to recon.

[cadetchris]

ill have a read of the manual and consult a specialist.

I would usually try and find a "good" replacement, but it took an age to find a wolseley 1500 one and i am really reluctant to get rid.

anyway, IF i decided to rebuild, what would i need to replace?

presumably bearings and gaskets do they have thrust washers in?

[bmcecosse]

Depends what you want to 'rebuild' - the 'diff' or the final drive? The diff has thrust washers and these do wear. the final drive has bearings - these are unlikely to be seriously worn unless they have been run without oil - or with contaminated oil........... Whining noise is likely to be the mis-alignment of the pinion to the helical gear - and maybe by adjusting this - you will minimise the noise. Read the Manual!

[IslipMinor]

Whine can be bearings and/or pinion to crownwheel alignment. Worn thrust washers inside the actual diff itself cause increased backlash between the diff and the halfshafts, but are not the source of whine, as there is only a limited amount of slow rotation when cornering. If it is only a slight whine I would just change the oil and leave it as is.

To do anything with either bearings or alignment needs a series of measuring tools, a dial gauge for the crownwheel backlash and a special height gauge for setting the pinion. All bar the height gauge are general engineering tools, but unless you either have these or have access to them and know what to do, a specialist is a very good idea! The full BMC Workshop Manual has complete details of the set-up procedure.

I had a slight whine and also grumbling when I wanted to fit a Tran-X LSD, but as I do not have the height gauge, or access to one, I did everything apart from change the pinion bearings on my 3.9 diff. The carrier bearings were worn and the diff cage alignment shims in the carrier had broken up, so when fitting the new diff, the pinion and bearings stayed in place and I replaced the carrier bearings and aligned the old crownwheel to the old pinion to give the correct backlash, using new shims. The slight grumbling noise disppeared, but there was and still is a very slight whine that is about the same as it was when I did the job 9 years ago!

[cadetchris]

well it has lots of new oil in it and the whine is still there. its annoying to say the least. well ill see if i can find a specialist company that can rebuild it totally for me, its evident that its not a job that can be done in the shed with a cup of tea nearby.
anyone know any good reputable companies that can rebuild it?

[bmcecosse]

Oh some have done it on a trial and error basis - just move the pinion slightly inwards towards the crownwheel and then refit and road test... You could be lucky first time !

[David53]

I am currently having my diff (MM type split case) rebuilt by a local firm. Older firm with original owner still working, lovely old chap who loves vintage cars. Turns out I have lost a tooth from the crownwheel, hence the "dub dub dub dub" noise (not pinion bearings at all!).

If you can find a good old fashioned place like this that would be my suggestion to you.

[bmcecosse]

I think even I with my failing eyesight could spot a missing tooth...........

[David53]

While its inside the axle?

[mike.perry]

I expect you could Roy but the tricky bit is shimming the MM diff and axle case. I have a collection of axles with broken crown wheel or pinnion teeth

[David53]

The fellow at the diff place told me the MM diff was very similar to an MG TC but with a smaller crow wheel

[IslipMinor]

Mike,

Just had a look at the BMC Manual for setting the MM diff up, and it is really not very nice! All sorts of special tools and gauges required. Makes the later axle seem positively child's play by comparison, but like the earlier axles, it still needs to be done properly to avoid noise and/or premature failure.

Anyone know where of one of the BMC tools 18G 191 and 18G 101A for the later axle might be available?

[bmcecosse]

This makes interesting reading and suggests a dimension for the setting block.
http://www.ntahc.org/techtips/REAREND1.html