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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Can I fit a 1500 diff into a 1098 rear axle ?

My now 1275 powered machine started life as a 1098, so has the low ratio rear axle. Therefore it revs - all the time so much that first and second are almost never used as they are too low, I'm sure I've read somewhere that all the diffs are the same and the ratios going from low to high are 1098, 1275, 1500 - is the correct ?

All this work cos the windblokker works and now I want to bom around Britain roads without the engine sitting at 5500rpm.

Ta.

Malc
Malc Gilliver

Yes all interchangeable.

1098 + early 1275 4.22.
later 1275 3.9
early 1500 3.9
later 1500 3.7

R.
richard boobier

I've got a 3.7 in a Frogeye axle which seems ok.

Rob
Rob aka MG Moneypit

I've got a 3.9 in my Frog and I had no problem getting it in other than the awkward position to lift it in.
Martin Washington

I recently saw that MGOC Spares is doing 3.7:1 crown wheel and pinion or in recon diff

"3.7:1 midget CROWN WHEEL AND PINION
Previously unavailable MGOC Spares has commissioned new 3.7:1 crown wheel & pinions (BTA535) manufactured to the original design and specified for use on Midget 1500 models. Owners of earlier MG Midgets & AH Sprites can benefit from upgrading to a 3.7:1 rear axle ratio, which will lower their car
Nigel Atkins

I think the recon units are a bargain (I got mine from Moss) because the setup procedure requires a lot of work and one or too workshop items I don't have.
Nick Nakorn

Thanks guys, I'll look into the fitting / setup procedure.

Malc
Malc Gilliver

Only 60 surcharge on the 3.7 diff. It would be worth putting on eBay rather than re-claim the surcharge with a returned diff.

Rob
Rob aka MG Moneypit

If you've a 3.9 diff in good order you could probably get at least double the surcharge if sold on ebay. Malc, it's an easy task fitting a new diff. Just a bit awkward when lifting the new one into position.
Dominic Excell

Have a look in the things for sale section of this forum there's usually one or two there. And if you buy from someone from here you're likely to get an honest appraisal of its condition
Andy Phillips (frankenfrog)

I believe my diff is 4.22:1 hence why I want to change it.

I'd assume that any surcharge would require me to provide the supplier with a diff of the same ratio ? does anybody know it that is correct - i.e. did anybody change a diff and get away with sending different ratio back ?

Thanks Andy - I'll have a look.

Malc
Malc Gilliver

Malc,

Where is the filler on your current axle? If it is in the alloy diff housing, you may find that you end up with no filler, as the 3.9 or 3.7 diff will most likely not have one - the filler is in the axle casing itself.

On the other hand an 'early' diff and 'late' axle casing will give you 2 fillers!

Worth checking before you find you have none.
Richard Wale

Thanks Richard,

Off to get my jack out.

Malc
Malc Gilliver

Richard: don't all axles have a filler in the banjo on the axle itself? My albeit limited experience with all three diff ratios suggests no filler on the diff itself because the axle banjo has filler, breather and drain.

Don't forget Malc if you change the diff you will need to replace or recalibrate your speedo, or put up with the error!
Graeme W

Graeme,

I understood that all spridgets had a filler on the axle casing.
Earlier models also had a second filler on the diff casing as it was needed on other BMC models that did not have the filler on the axle.
It was deleted from the diff carrier on later cars.

As diff's are interchangeable within many BMC models it is possible to find a diff filler on various ratios.

R.
richard boobier

Yes, all Spridget axles had the filler plug.

A30 and A35 axle casings did not have the filler plug, it was in the diff.

Very late 1500 axles have no drain plug!
Dave O'Neill 2

Dave,

I think Wolseley and Riley 1500's may have had the filler in the diff also.

R.
richard boobier

Richard

You are more than likely correct.

I have had a few Riley diffs with the filler plugs in, but I've never actually seen the axle case.
Dave O'Neill 2

Does anybody know a good axle reconditioning company, ideally in the Midlands ?

I can see a Sprite and MGB axle rebuild on my near horizon....

Malc
Malc Gilliver

I can't think of anyone in the Midlands.

There is Hardy Engineering in Surrey.
Dave O'Neill 2

Hardy make a good job of diff rebuilds by reputation and by my experience. Not cheap (dont know what others charge) but setting up with new bearings will cost around 150 IIRC. Crown wheel and pinion replacement would add substantially more.

I don't know how good the quality of the MGOC items is, but I know someone who bought a unit from Heathrow Transmissions and he is quite happy with it.

Graeme W

Malc,
how about asking Klassik Transmissions if they know anyone local - http://www.klassiktrans.co.uk/
Nigel Atkins

Nigel,

Great minds and all that - Ken at Klassic rebuilt my gearbox - emailed them yesterday - he has given me a phone number to try.

Malc
Malc Gilliver

Malc,
I'd suggest you start to worry if you ever think like me - at least I was late suggesting it, I did actually think of it yesterday but couldn't remember if they were in that neck of the woods
Nigel Atkins

This thread was discussed between 27/06/2014 and 12/07/2014

MG Midget and Sprite Technical index

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