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MG MGA - Differential

I've been working on my differential replacing the thrust washers and whilst doing this noticed a puzzling difference between the shape of my aluminum diff housing and that shown in Clausanger's book page 70. The picture shows the top of the housing with a raised stiffener that goes all the way from the axle to the flange. For the record this is same as shown in the Moss catalogue page 29. In my diff this stiffener stops short of the flange and there is a small rib that then carries on to the flange. Curiously if I turned my diff upside down it would look similiar to the Clausanger picture but the diff can I assume only go in one way with the crown wheel on the right of the pinion as you look back at it. I always thought that the diff housing was unchanged throughout the production run but maybe not?
J H Cole

Heres a picture of my diff showing the small rib at the flange end.

J H Cole

Hmm! Your picture looks like the 3.9 carrier I pulled from an early MGB.
James Johanski

JH--I checked the castings on both of my MGA differentials and they are like the pictures in Moss, the parts manual, and Clausager. The MGB differential casting is like the one you have pictured. What is the rear axle ratio? Perhaps this casting is from a Magnette. Anyway your has the gear set mounted the proper way (it can only go in there one way) and the is pictured correctly for installatiion. Hope that helps.
James Johanski

JJ, I've got a Mk 2 so the ratio is 4.1 to 1, not 4.3. Perhaps this caused the different casting shape. I know its the same as the MGB with 3.9 ratio. The late Mk 2's must have gone with the different shape.
J H Cole

John

Out of my idle curiosity, have you counted the crown wheel teeth to confitm your gear ratio?. As with James above, your carrier is the same as mine (MGB 3.9). The only reasonable explanation for this to migrate to your car would have been for a previous owner wishing to convert the ratio.

Steve
Steve Gyles

Steve, I checked the crown wheel and its got 41 teeth which is correct given the 10 teeth on the pinion. I'm still of the mind that the Mk2 diff is a different casting to the 1600 and this diff was carried forward to the early mgb's except with a 3.9 crown wheel. Are there any Mk2 owners with a 4.1 diff with the earlier casting?
J H Cole

John

Most interesting. Let's see what other Mk II owners find. Fascinating what these investigations throw up in the way MG used common parts bins to keep production lines rolling.

Steve
Steve Gyles

My fairly late Mk2, chassis #108354 with its original 4.1, has the later style differential housing as shown in JH's photo.

Garry
Garry Kemm

My Mk2 (Australian build) has no rib, nor does the spare 4.1 diff I have. Jim.
jim mckenzie

This thread was discussed between 03/05/2008 and 11/05/2008

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