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MG Midget and Sprite Technical - Gearbox swap

I am thinking of changing Bugeye gearbox from the original smooth case to a later rib case close ratio box. I assume that I will also need to change to the later type diaphram clutch? Is there any other mods I will need to do ?
Noel Copping

BMC suggested that in making this change a 1098 backplate,flywheel,and 7.5 clutch unit were used.
I am however aware of people just bolting on a 1275 - 6.5inch clutch and experimenting with the slave cylinder pushrod lengths.
Alan.
A Anstead

The 1275 clutch won't just bolt on, as the flywheel needs to be re-drilled.
Dave O'Neill2

Further to David's comment the bolt pattern is the same IIRC but the 948 clutch cover has 2 locating dowels and the 1275 diaphragm cover has 3 so 2 new dowel holes need to be provided and the assembly balanced.
David Billington

David, the bolt pattern is not the same. The 948 has six bolts equally spaced, the 1275 has them grouped in three pairs.
Dave O'Neill2

Thanks Guys,looks like I need to change flywheel as well.
Noel Copping

Unfortunately, you can't just fit a 1275 flywheel, either.

948 flywheel is secured with four bolts, 1275 has six bolts and two dowels, and the flange is different.

I don't see why you can't keep the original clutch, or even change to the uprated 9-spring version.
Dave O'Neill2

This thread was discussed between 27/11/2011 and 29/11/2011

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