Differentials & Diff Covers

The differential splits drive between the two driven wheels and lets them turn at different speeds in a corner. The parts here concern how it is held: a rear differential mount, and a carrier stud kit that clamps the gear carrier into a removable-centre axle housing.

Whenever power goes down, the differential housing is twisted in its mounts by the torque it passes on. With independent rear suspension, rubber mounts hold it and let it move, which adds driveline slack, clunks on throttle changes and can feed wheel hop. A firmer mount holds the housing steadier, at the cost of more gear whine and vibration in the cabin.

On a removable-centre axle, a ring of studs and nuts clamps the carrier to the housing. Under high torque the joint tries to flex, and stretched fasteners let it move and leak. Studs in a stronger alloy steel can be tightened to a higher clamp load, which keeps the joint closed.

What to check:

• Stud kit: 8740 chrome moly press-in studs with a round head, a knurled shank and 3/8-24 threads, and hex nuts that take a 9/16 socket.
• Mount: the differential mount is listed for named models, so match the title.
• Use: launches and track work load both parts hardest, while on a road car replacing cracked or soft rubber is often enough.

Press each stud fully home in the housing flange, with its head seated flat, before the carrier goes back on. Use the lubricant the stud maker specifies, because the torque figure depends on it, and tighten the nuts in a cross pattern in stages. Seal the joint as the axle maker specifies, refill with the correct oil and check for leaks after the first run. When changing the mount, support the differential, then recheck its bolts after a few drives.