[patrickt]

I have the same ratchety noise problem in my ERA rear. From the manual:

Differential: The filler and drain plugs are ½” square. Fill
with Moroso climbing gear lube, SAE 90, part number
34800, mixed with 4 to 8 oz. of Amalie limited slip additive
(part # 505-6775). If the above are not available, you may
use 80W-90 GL5 lubricant with an equivalent limited slip
additive. If the limited slip seems to be sticking (ratcheting
around sharp corners), drain and refill, replacing the
Amalie additive with 2 tubes of GM additive 1052358.

Question: Is there any danger in overfilling the differential and stressing the seals? Or do you just take it up to the bottom of the fill hole and that's it.