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MG Midget and Sprite Technical - Differential failure?

I am new to MGs as I recently bought a 1978 1500 midget. This weekend I had total loss of drive to the wheels with fairly horrendous grinding which sounded like from the rear of the vehicle. When I got it jacked up the off side wheel drives the prop shaft when rotated but the near side freewheels and there is a grinding noise from the diff. Can I assume that the diff is completely gone and have to buy a recon or should I do more investigation? Thanks
R Hillman

Broken half shaft ? Remove the wheel and brake drum then pull the half shaft out. They commonly break at the splined end where they fit into the diff. If you're lucky it will just pull out
Andy Phillips (frankenfrog)

Ok. thanks for that. I'll give it a go!
R Hillman

If it is broken then you need to take out the other side so that you can then remove the diff. Check the diff for damage then thoroughly clean diff and inside of axle housing before re assembly. New updated half shafts are available from magic midget or peter May or other places. Don't forget to drain your axle oil first
Andy Phillips (frankenfrog)

I have some standard halfshafts available, if you find you need one.

daveo138 at yahoo co uk

Also use a magnet to pick up any stray pieces of metal in the axle casing.
Dave O'Neill 2

Broken half shafts are a possibility but they don't tend to be that noisy. If the grinding sound is loud it could be a broken crownwheel carrier. Cracked carriers are common in these diffs. See image.

If so, the CW&P would probably not be damaged but fitting another carrier requires a bit of expertise in setting up. Crack test the "new" carrier before fitting and grind smooth the area where cracks start.

Bob Schapel

R L Schapel

Could also be the planetary gears. Mine made a grinding noise when they failed. If so, when you replace them, make sure you replace the sun gears also since they are probably damaged.

Martin Washington

Ouch!
graeme jackson

Yeah, that was my reaction too. The gear that;s missing came out in three pieces and the sun gears had divots in some of the teeth. The only place I could find replacements was at MGOC. Moss and MiniMania list them but as N/A.
Martin Washington

If it turns out to be the planetary gears try to get some locally. However if you have trouble I can help but will have to post them from Australia assuming it is the 10 spline type you want. They are the usual type.

I have a carton full of them, probably more than 50 sets. (wired in sets .. see image). I used to convert Spridget diffs to fit TCs (and I have done a couple for Y-Types). The conversion involved removal of the Spridget planetary and sun gears. A few sets are worn but with that number to select from !!!! If you have the fine spline (25 spline ?) type I might have a set but not sure.

Good luck with it. I suspect carrier but hope not!

Bob Schapel

R L Schapel

following on from Bob, I have spare s/h planet gears here in UK (and usually spare complete diffs if needed).
David Smith

Bob

Conversion of Spridget diffs for MG TCs sounds interesting. Guess for parts availability reasons? Why no more - parts available to rebuild TC diffs and axles, or you'd had enough of doing the conversion?

Cheers
Mike
M Wood

Mike,

Spridget/Morris diffs became harder to find and more expensive. Half of them had cracked carriers. It was mainly Morris diffs I converted as the ratios were good for TCs (4.875 and 4.55) but the other taller ratios were good for racing TCs. I also designed and made rear crank seals for T-types from about the mid 80s. Wasn't spending enough time on my own cars.

Bob Schapel
R L Schapel

Hi Bob

Thanks, interesting info. Useful to know if I ever manage to locate a rough T Series for rebuild for hillclimb/sprint racing ion a budget (missed that boat 30 years ago!)

Cheers
Mike
M Wood

Mr R Hillman,

What did you find. Was it an axle? planetary gears? I am curious to know. I hope your repairs are going well.

Mike, yes there are 8 ratios available in these diffs! Very versatile bits!

Bob Schapel
R L Schapel

Thanks for all of the advice! I pulled out the near side half shaft and half of the spline and most of the teeth were missing. Pulled the other side, drained oil (including the rest of the teeth and a fair amount of swarf) then rebuilt using a "new" half shaft from MGBeehive. My first proper job on the Midget and it was pure pleasure. All good now: thanks again for all of the advice!

R Hillman

Thanks for the report. I had wondered what you found. I bet it's great to be back on the road!

Bob
R L Schapel

Good to hear that it was the "easyist" of the possible failures. Pretty soon you'll be rebuilding engines and gearboxes.
Martin Washington

This thread was discussed between 01/09/2014 and 16/09/2014

MG Midget and Sprite Technical index

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