Hello I have an 89 N/A and I just replaced the gear oil in both the tranny and dif.
GL-4 75-90 for the tranny and GL-5 75-90 for the dif, filled both to the appropriate levels.

When I got home today and backed up it sounded like the dif groaned. I'm not positive where the noise came from, it sounded like worn out pads on scorched rotors. The noise wasn't constant it just let out a groan and stopped.

I know thats not too descriptive but any ideas?

Thanks.

 

mine does that too, and a lot of other manuals i have driven, it might be normal, im not sure, but just a thought