Switch To 75w-90

01silverado2500 · March 23, 2007

I see the book calls for 80W-90 oil in the front diff. I am going to be servicing my dads 06 Duramax diffs and they both take 75W-90 Synethic. Can I switch my front diff to Synthetic 75W-90 just like my rear is?

Truck is a 2005 1500 Sierra with AutoTrac and the G80. I checked and it already has the white vent cap for the synethic fluid.

Also, should I stick with the $25 + GM Syn Grape Juce or should I use the Mobil 1 Syn oil?

wct · March 24, 2007

I'm not sure were your from but if you live in a cold climate condition I would strongly recommend making the switch. It certainly won't hurt any thing. As far as what brand I think it would probably be a personal preference, I would use gm but that is what I prefer. WCT

01silverado2500 · March 24, 2007

I'm not sure were your from but if you live in a cold climate condition I would strongly recommend making the switch. It certainly won't hurt any thing. As far as what brand I think it would probably be a personal preference, I would use gm but that is what I prefer. WCT

SW PA here near Pittsburgh. Truck lives outside year round and there were a few zero degrees here this last winter.

I just wanna know if the 75W-90 Syn would have any problems with the Atottrac over the factory 80W-90. Thats all Im really worried about.

wct · March 24, 2007

I'm not sure were your from but if you live in a cold climate condition I would strongly recommend making the switch. It certainly won't hurt any thing. As far as what brand I think it would probably be a personal preference, I would use gm but that is what I prefer. WCT

SW PA here near Pittsburgh. Truck lives outside year round and there were a few zero degrees here this last winter.

I just wanna know if the 75W-90 Syn would have any problems with the Atottrac over the factory 80W-90. That's all Im really worried about.

You are talking about the transfer case right? when you say autotrac. The syn. is actually better for the t-case w/ auto 4x4 the syn responds to the cold climate better than regular 80w90 and provides less resistance in the front differential witch would be better on the clutch pack in the t-case. hope this helps you out. WCT

superbee · March 24, 2007

If you have autotrac, grape juice is the only thing you can run in the tcase. 75w-90 synthetic is just fine in the front diff, 75w-90 Amsoil is in my HD and the wife's burban. I have the same weather as you.

wct · March 24, 2007

If you have autotrac, grape juice is the only thing you can run in the tcase. 75w-90 synthetic is just fine in the front diff, 75w-90 Amsoil is in my HD and the wife's burban. I have the same weather as you.

I sorry, I didn't really clarify that very well but that is what I meant in the front diffy 75w-90 and auto trac fluid in the t-case, But the syn in in the front diff would be easier on the transfer case clutch pack do to the less resistance of the front differential. my bad thanks superbee - WCT

01silverado2500 · March 25, 2007

So looks like I am gonna switch to the Syn 75W-80 in the front diff. I will not be changing any of the transfer case fluid, I know it takes the special blue autotrac fluid. I just dont wanna change the front diff to syn and cause damage to my transfercase in any way.