So with my '02 approaching the 100k mile mark, I was thinking I should change-out the fluids in both front and rear diffs and the T-case.

I have read that since I have a 4 button 4x4 switch that the T-case requires GM Autotrak fluid...is this correct? How about the fluids for the front and rear diffs?...what goes in these? Is the GM posi fluid required for these?

Appreciate any info.

Thanks in advance.

 

Auto-trak II it is about $12/qt and you will need 2 quarts.

 

^^X2, gotta use Auto-trakII fluid, (GM dealer) in 4 button, (NV236) transfer case. It has an oil pump and a clutch pack inside, and if you don't use Auto-trak fluid, you'll have expensive problems. 80w90 fluid in both differentials, posi track fluid is not necessary.

 

Got it....use Auto-Trak fluid in the T-case and just normal 80W-90 in both diffs.

Thanks for the answers. I am going to get a new cover seal for the rear and drain the old fluid out that way. Gots lots of time.....I only put 5k miles a year on the Blazer...so likely will be this time next year before I do this job.

Thanks again.

 

Checked RockAuto for a rear diff seal and there are two listed, one for a 7.625" RG and one for a 8.625" RG, both 10 bolts. Is there a way to tell what the RG size is without taking the cover off?

 

I just use a bead of RTV. Black seems to work great.

 

Use the chart on this page for identifying GM differentials:
Dana Differential.

 

Thanks for the chart Captain and I guess just RTV would work as well.

 

RTV would probably cost more than the correct gasket! Might want to think about replacing the cover as well, (they like to rust out). Dorman makes them, which means most auto parts stores either have it, or can get it.

 

Thanks again Captain. I will most likely replace the gasket and will check the cover condition; no rust here in Tucson, but Blazer came from Long Island.

Looked at the cover, although the spare is still in place, so difficult to see the entire cover; but I think it appears to be the Dana 25, 27, 30 from the picture in the link above. But it could also be the GM 7.5, 7.625...again difficult to tell for sure with spare in place.