do i need to service my posi rearend?

[Oaktown]

my 87 gn has 156k orig. miles on it and i cant trust that any of the former owners have even touched the rear end. i know that these cars get "sideways" when that turbo kicks in...although my gn doesnt, it never does really...it is a posi i know b/c it says limited slip on the original receipt...i guess maybe my clutches are worn or something...please give me some insight on the rear end...maybe what is wrong with it...how i can fix it? do i just need to put a new seal and new fluid or does it need repair?

 

[MistaScott]

First, be sure it says G80 under the trunk with all the codes. It can be "limited slip" and not posi. Most GNs were posi so you probably have it but just be sure.

Differential fluid needs to be serviced regularly IMO. I'd say every 8-10K miles it should be changed, some say it can go longer, like 100K. I hope previous owners serviced the rear end at least once. It is a definite maintenance item. To service, you have to take the cap off and then drain the fluid. It is a mess. Then you refill it and put a new gasket on. If you can hear your gears in the rear then its time to change the fluid.

 

[MARINES185]

If you have a limited slip rearend then you have posi because
posi and limited slip are the same thing just different names. as
far as checking your posi jack up one side of the rear leaving
one tire on the ground.place trans in neutral. try turning
the wheel thats off the ground.if it turns freely then you
either don't have a posi rear or the clutches are toasted
in your posi unit. if you can't turn it by hand then you have
posi. if you put a torque on that wheel and start turning
it the posi unit should start to slip at 35ft.lbs.