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MG Midget and Sprite Technical - Da Diff Dead?

If I have a bit of a hammy gear change (it happens more than I care to admit) or boot the accelerator from low speed in a low gear there is a nasty clunk from behind me.

It seems worse when cold, setting off from my drive I can't shift 1st to 2nd without a big clonk.

Prop shaft UJs were replaced during restoration.

Only pic I could find from when it was apart, these teeth look a bit mangled.

I suspect I know the answer already, should I be asking for a new diff for my birthday this summer?!

Cheers,
Malcolm

Malcolm Le Chevalier

Oil when it was drained during restoration.

The car has done in the region of 95,000 miles, I can only assume the diff is the original.

Malcolm Le Chevalier

What diff is it. I've seen many of the later diffs which used tufnol sun gear washers where the only bit left was in the radius at the base of the gear boss. That'll increase the running clearances of the gears somewhat. The earlier bronze, and I've seen some steel thrusts, fared much better with little measurable wear after long mileages.
David Billington

Its a 1976 3.9 Dave.
Malcolm Le Chevalier

Malcolm,

I would expect it to have tufnol washer then behind the sun gears and it's very likely they have worn away to nothing. If you pull it you should be able to check visually or with a feeler gauge I expect.
David Billington

Good knowledge David, thanks. If I am going to pull it I am going to line have a replacement to go in. I don't want to be off the road for weeks. Do you know anyone?

I think I will get some half shafts "growlerised" to go with it too.

Malc
Malcolm Le Chevalier

Hi Malcolm,

If you need replacement gears and have trouble getting them in U.K, I have a big carton full to select from, wired together in sets. I used to convert the diffs from Morris, Spridget etc to fit MG TCs and in the process, the spider gears were not used. The sungear washers were used in the TC conversion but I am sure I would have some of those also (bronze). I sent a set of gears to Les Robinson in UK about 6 months ago and from memory got $70AU for them. Can't remember postage but it was only about $10AU.

Bob Schapel (South Australia)
R L Schapel

Malcolm,

Looking closely at your first image, it could be the edge of a tufnol washer I can see behind the sun gear.

I hope it is my imagination but when I look closely at the carrier very near the threaded crown-wheel hole I see something which could be a crack. (About 5mm from the threaded hole on my screen.) During my conversion of about 45 diffs, (and dismantling many more for parts), cracks in exactly that position were something I encountered often. Because the crack works progressively into thicker metal, I only saw a few carriers which were broken through completely. I have included an image of a cracked carrier. I normally use a proper spray on crack test but the only image in my computer files is not the genuine stuff but an experiment of fungal foot spray after a clean with paint thinners!!!

How bad is the "clunk?" If the carrier is broken I would expect some gear noise too as the mesh would be compromised.

I hope the problem turns out to be simple to fix.

Bob Schapel

R L Schapel

This thread was discussed between 06/05/2016 and 07/05/2016

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