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MG Midget and Sprite Technical - Ford diff in a Sprite axle casing

I have somewhere that it is possible to fit Ford CWP into a Sprite back axle . Or was it the whole diff housing into the axle case? Can somebody point me in the right direction as to the technical details behind this.
Also what is the most safe power you could put through a sprite axle assuming you had say Peter May halfshafts , what would be the next weakest link, the CWP or the sun gears?.

Thanks Roy
R Mcknight

It's normally a whole shortened ford axle, but I sit to be corrected on that :)

As for most power - some of the K-chaps are putting 170bhp+ through standard diffs. I've seen the result of the diff internals all coming to bits on a 180bhp+ car.

Mine has around 110 and gets mercilessly abused on the standard shafts and diff, and has been OK so far.

I think it depends on how worn the stuff is to start with, and the degree of mechanical sympathy that's employed. I'd say (GUESS!!) for road use the standard stuff would be OK up to about 120 130 ish if not being too fierce with it.
Rob Armstrong

The only one I know of using the Ford diff was Simon Page's Turbo race car - but he ran an Anglia Axle complete. I'm sure there were others similar, but I haven't heard of any using a combination.
Mark Lister

I posted the plans for doing the job a few years ago. Not sure if I kept a copy. You use the Ford bits from the very heart of the diff and stick the CWP from the midget onto them. You then adapt the ford halfshafts to fit the Midget hubs and bearings. You keep the CW&P and really only bin the Midget planetary wheels and bits in that area.

David Vizard developed it along with Ray(?) Mallock.
r thomas

Roy
Assuming you have halfshafts that are up to it, the most vulnerable part of the standard diff is the lack of lubrication to the planet gears during wheel spin. This causes them to seize on to their shaft, then one shatters as they are trying to run the shaft in opposite directions.

If you avoid wheel spin, they appear to be OK. This involves care with the right foot, or fitting a limited slip diff. Going down the latter route is probably simpler than fitting the Ford internals, and has the usual LSD advantages in addition to greater reliability.

Our current diff, Midget CW&P on LSD, has done 10 years+ of serious autotesting (much tougher on diffs than racing) delivering 185BHP from our K for moswt of the time, more (especially more torque) for the last couple of years since we added a supercharger.

With the LSD you can also specify fine spline sun gears which enable a much stronger design of halfshaft.
Paul Walbran

Rob is correct; there was an article on this in Car Mechanics or CCC about 20 year ago. I think I have a copy filed away but I'm currently in the southern hemisphere so cannot look it up.
David Smith

>> This causes them to seize on to their shaft, then one shatters as they are trying to run the shaft in opposite directions

My experience exactly at Martini uphll right-hander (Wiscombe), except I eventually lifted off (I guess I was over the line!), and carried on driving. When I arrived home later, I could hear a clang from the diff when driving slowly... turned out that the retaining pin on the diff/planet shaft had been sheared the the shaft was clouting the pinion...

Russ, on at least one occasion, milled his pinion against th crown until is had mere (and extremely sharp!) slivvers left. I have pics.

With the A Series engine, it was WOT or nothing; I had to learn how to feather with the K...

Anthony
Anthony Cutler

IIRC it is also possible to fit the entire Ford final drive unit into the sprite axle but requires re-drilling to suit the Ford pattern and making a spacer to get the sun gears in the right location for the half shafts.
David Billington

have a look at what Turner Cars used to do.
PeterJMoore

Found it!




r thomas

This thread was discussed between 04/03/2013 and 12/03/2013

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