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MG MGA - Riley gearbox

I need to dispose of what I'm told is a Riley gearbox that looks a little like an MGA box. Does anyone recognize it and would there be any compatible parts that might be worth keeping for the MGA?


J H Cole

If the Riley had a B series engine then probably all of the internals will be the same as the A box. The only way to find out is to take it apart and see!
dominic clancy

Cute. Front and rear housings, side cover and shifter mount are different. My guess is that everything inside is interchangeable with the MGA parts. The tail end seal is similar to MGA mid 1500 type gearbox, so maybe the 3rd motion shaft is that type.

Pull the side cover and count the gear teeth to verify that the gear ratios may be same as for MGA. See here: http://mgaguru.com/mgtech/gearbox/gt102a.htm
Barney Gaylord

I think that I had a couple of these gearboxes once, they were out of a Riley one and a half, if I recall. I think that they are similar to an MGA but with slightly different indirect ratios.
Barry Bahnisch

I looked at the two WSMs out of curiosity. The gearbox ratios are the same, but as the 1.5 used the A series rear axle, the final drive ratios are different. That means the innards should be mostly re-usable in an A gearbox
dominic clancy

With that type rear seal it should have 1-1/16" diameter 10-spline output shaft, and all internal parts same as the MGA mid-1500 gearbox. It might have different speedometer drive gears due to higher ratio final drive in the Riley.
Barney Gaylord

Is it the case when one refers to a 1500 box its only the casing that differs from a MK 2 box? My box is in need of a rebuild (whining first gear but not yet jumping out)
and if the Riley innards are in reasonable shape is it a sensible proposition to do a swap of the various bits that are good?
J H Cole

You may find that the parts in the Riley box are also worn, but the only way to find out is to take it apart and have a look. If it is Ok then the innards should be useable to fix your own box.

If the parts are worse than your original MGA box, then at least you have had some practice for the rebuild!
dominic clancy

There are three different rear housings for MGA, and three different mainshafts to match (as well as three different propshafts). You cannot change type of rear housing and propshaft without also changing the mainshaft.
Barney Gaylord

Senior moment, I suspect. I was thinking of an earlier Riley gearbox, which looked similar to a TC, as I recall.
Barry Bahnisch

This thread was discussed between 29/06/2013 and 02/07/2013

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