Hi all i need to change the rear end fluid in my 85 z28 got a few questions before i screw it up lol.

what weight gear oil do i buy?

do i need a posi additive? (when i bought the car the guy said it was a 3:23 posi i can't tell. sometimes when i light up the tires from a standstill they both spin other times only one will spin so is it posi or no? if so any autopart store will have it?

im pretty sure the cover is leaking so when i put the cover back on do i use a gasket or no? (i heard of some people not useing the gasket.?

 

use the posi additive if you have a clutch type posi, i'd only use additive from gm. yes use a gasket reguardless of what "other people" do. i use mobil1 or amsoil synthetic and i think both are 75w-90, or something very close to that. no problems yet.

 

sometime the rears have a metal tag on them. it should be bolted on the cover.