Chicagoland MG Club:Photos
MGA Differential Swap
Changing the 4.300:1 gears to 3.909:1

June 3, 2001
- St. Charles, IL
Page 1 of 3

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Steve Merical already had the rear of his MGA up on stands, and the wheels and brake drums removed by the time the help began arriving. The half shafts were easy, just one screw, tap a knife blade into the joint and give a little tug. Since it was this far disassembled, we might as well change the hub seals while we're at it. So straighten the lock tab washer a bit, use that special HUGE tube socket to remove the 1-61/64 octagonal nut, and then remove the locktab washer.


The first hub nut was not particularly tight (as is often the case). As a result, the wheel bearing was also not particularly tight on the axle housing and could be easily pulled off by hand. The seal surface on the axle housing was clean and smooth, no grooving there (lucky this time), otherwise a Speedi-Sleeve might be required to repair the surface. Time to scrape off the old paper gasket and remove the flattened rubber o-ring from the hub.


With these hubs the wheel bearing has to be removed in order to R&R the rubber hub seal, which is in a blind counterbore behind it. Once the new seal is installed, and the big bearing back in place, you can install the new rubber o-ring seal and paper gasket. Then push the bearing and hub assembly back onto the axle housing and install the locktab washer. These locktabs can be reused a couple of times. Just hammer the edges flat, and then bend it up in a different place the next time.


The large nut is a little chipped and battered around the edges. This was done by one (or more) previous mechanics who thought a chisel and hammer was a good substitute for the octagonal socket when they didn't have one of those handy, which is why these nuts are often not properly tightened. But nothing serious in this case, still flat on both sides, clean thread and no big burrs, so good enough to be reused. We use a long tire iron through the cross hole in the big socket and lean on it pretty hard to tighten the big nut. Then on to the other side of the car where we find a little more damage to the large nut, enough to make us want to replace it.


The left side hub nut has left hand threads. Very early MGA 1500s, the first 11,000+ cars, had right hand threads for both sides, but all later cars used left hand threads on the left side. This one was substantially tighter (as it should be), so the bearing was being held securely on the axle housing and would never move in operation for many years. As such the inner bearing race was snug on the axle housing and in need of some mechanical encouragement. Many slide hammer kits will have a special fixture made just for this job. Attach the puller yoke to the hub with a couple of backwards lug nuts, and a couple of quick pulls of the slide hammer pulls the hub assembly right off the axle housing, no problem.


Once again a nice smooth seal surface on the axle housing. We rather expected that after seeing the first one. Meanwhile Steve is working at retrieving a better left handed bearing nut from another rear axle assembly, while other hands are installing the new hub seal for the left side. The rest is just a repeat of the first, reassemble with a new o-ring and paper gasket, torque the big nut for all it's worth and bend up the lock tab.

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