What grade of gear oil for the diff.

I am planning on changing my differential gear oil to see if that helps with the thumping from the rear when I making turn. But, don't know what grade to use and how much.

Plus, I'm also flushing the TC and changing the transmission filter and fluid. I know how much to use (13 qts), but I don't know what type of fluid to use.

Thanks,

Read your other post for additional info on your diff. Your owners manual should tell you the weight of the oil. 80/90 should be it, just double check.

As far as the tranny goes...Normally receives Mercon III but many suggest Mercon 5.

What year? After 93 I would use Mercon 5 and 3 if its before.