Rebuilding a diff

[alainmoran]

So I've come to rebuild my diff and found some false fingernail shaped & sized slivers of copper in the bottom, also there appears to be a copper spacer behind one of the sun-gears but not behind the other.

My question is are these sized to fit the gears like shims? How do I tell what size I need?

Where do I buy them?

Both planet & sun gears are pretty worn, is there anything that can be done given that nowhere seems to stock them.

[MarkyB]

Given how complex and needing of special tools this job is and that the major bits are badly worn already I'd say find a decent used unit.

[Mogwai]

Looks like the thrust washers are available but no gears on the moss site http://www.moss-europe.co.uk/Shop/ViewP ... exID=11636

you'll only need any special tools if replacing bearings or crownwheel/pinion etc. its quite easy to dismantle the planet/sun gears something Ive done is swap them out of a scrap diff to make one good one (same fault as you describe)

[alainmoran]

The crownwheel & pinion look in good condition and to be honest I'm going to stick with the sun & planet gears I have as they do work (mesh with each other) but are a little worn (slight step in the teeth) ... however given that they only ever get any use when you are turning corners I'm going to risk it for a biscuit

I'm interested to hear that I may need special tools to replace the bearings though - both the pinion & diff bearings seem pretty straightforward enough to remove/replace .. but then maybe I'm missing some vital piece of information

[bmcecosse]

I think the skill/special tools lies in setting it all up! If it's just a very ordinary 4.55 or 4.22 diff I agree that a good used unit may be the best way forward. However it is all well explained in page H8 onwards in the workshop manual if you want to make a 'project' of it! If the little gears are worn/stepped it may be wise to try to put them back in exactly as they came out or there may be extreme rapid wear in use!!

[alainmoran]

What would be the point in owning a minor if it wasn't a project

The diff is labelled BTA 548 on the casting, but ATA 7034 on the differential bearing clamps. The pinion has 9 teeth and the crownwheel 38.

Yes I see what you mean about ensuring I get the gears back in the same way as they came out, the wear on them will be in a matched pair arrangement ... that said there is a partial diff on ebay at the moment which I'm considering getting if you think it's probably worth trying it to see if the sun/planets are in better condition than mine.

[bmcecosse]

Good 4.22 diffs are plentiful! If buying another - try to get a 3.9 or even a 3.7 at the 'right' price!

[alainmoran]

In all honesty the plan is to rebuild this diff and the spare gearbox, and then swap them for the ones which are on the car at the moment and then rebuild those too!

Other than the dampers & the bottom end of the engine I've stripped & rebuilt everything else - I want to have experience of doing every single job on the car (as well as making sure everything is nice & happy), and I have a spare engine which I'm planning on blueprinting before I stick it back in ... not for any good reason other than its something I want to do

[bmcecosse]

Enjoy!

[alainmoran]

Fitted the rebuilt diff at the weekend ... all I changed in the end was the oil seal, the thrust washers and swapped the planet & sun gears for a set I picked up on ebay ...the nasty noise has gone, and all you can hear now is the gearbox

After stripping the nasty-noise diff it would appear that the differential bearings are stuffed, suprisingly after a cursory inspection the pinion bearings seem fine.