Gear Oil

[javojjaaf]

got a 98' Z71 and its time to change the diff oil along with the transfer case oil. anyone know what weight i should use in each and do i need any kind of conditioner for any? thanks

[Black02Silverado]

You need a 75w-90 gear oil for both front and rear differentials. Do you know if you have the auto push button transfer case or a manual transfer case. If you have the auto you need to go to the dealer and get the Auto TracII fluid. If you have the manual then it takes Dexron ATF. As for additives for the rear diff if you have a LS differential if you use AMSOIL's gear oil then you do not need to add any friction modifier. If you use Mobil 1 or another brand then you would have to find out if it is needed when using their fluid.

[javojjaaf]

yeah i do have the auto transfer case, so ill get the auto tracII. i almost positive that i have the limited slip as well, but cant i tell by an identifier in the glove box or some other place?

[Black02Silverado]

There should be a code for your rear diff, not sure how far back the G80 went in years. If you have that option then you have the G80 setup and it does not require a friction modifier.

[javojjaaf]

come to find out i do have a G80 locker!!! i am stoked about having it in a 98. i used this web sight to enter my vin and found out everything about my truck.... http://www.compnine.com

[javojjaaf]

There should be a code for your rear diff, not sure how far back the G80 went in years. If you have that option then you have the G80 setup and it does not require a friction modifier.

 

so, the G80 does not need the friction modifier? reason i ask is i just watched a demo of the diff and it has clutch packs in it, unless they changed it sense mine.

[Black02Silverado]

There should be a code for your rear diff, not sure how far back the G80 went in years. If you have that option then you have the G80 setup and it does not require a friction modifier.

 

so, the G80 does not need the friction modifier? reason i ask is i just watched a demo of the diff and it has clutch packs in it, unless they changed it sense mine.

 

 

 

If you have the G80 then you do not need any additive in the gear oil. Only the limited slip differential needs the friction modifier, not the mechanical locking diff, ie. G80.

[javojjaaf]

There should be a code for your rear diff, not sure how far back the G80 went in years. If you have that option then you have the G80 setup and it does not require a friction modifier.

 

so, the G80 does not need the friction modifier? reason i ask is i just watched a demo of the diff and it has clutch packs in it, unless they changed it sense mine.

 

 

 

If you have the G80 then you do not need any additive in the gear oil. Only the limited slip differential needs the friction modifier, not the mechanical locking diff, ie. G80.

 

 

i understand, its just strange that it has clutch packs...which i didnt know till i watched the demo.

[rodram]

the G80 in your truck is the Eaton locker ... do not put any modifier or additive in the rear differential ... just use 75W90 gear oil... adding limited slip additive may actually harm the locker and cause it to fail...

 

now the confusing part for some is that GM also calls the limited slip rear in some cars a G80 .... but any GM truck with a G80 will have the rear locker ... NOT a limited slip