Rear Diff Stuff

[Phone Man]

Hey guys. I want to change out the fluids and also change diff covers. I'm pretty sure the rear is 8.5 but what is the front? Also anyone partial to a specific brand of fluid?

 

[SunlitComet]

8.25, 80w-90 gl-5 or 75w-90 synthetic if you are in cold climate. tho i see no reason not to have it all the time.

 

[bowtiefreak]

if you have a trutrac do not use synthetic though. But Sun is correct.

 

[Donnie Yukonie]

if you have a trutrac do not use synthetic though. But Sun is correct.

why not?

 

[SunlitComet]

i believe bow tie is talking about a locker. but since you don't have one in the front axle synthetic should be fine.

you thread title indicates you are asking about the rear when actually asking about the front.

 

[Phone Man]

Sorry for the confusion. Was asking about both I guess. So If I only have the G80 in the rear i can use synthetic? And i've read not to use any posi additive, correct? I'm going to order a new cover today and change out fluids this weekend. Thanks for the info gentlemen.

 

[bowtiefreak]

why not?

Makes them chatter / noisy. That's all. Manufacturer says to use regular gear oil.

As for the G80, I forget but I thought it did want an additive. I'd double check it though

 

[Phone Man]

I'm finding that the advice is NO ADDITIVE for G80's in trucks.

 

[bowtiefreak]

worst case it doesn't lock up, not really a bad thing for a G80

 

[SunlitComet]

G80 uses no additive as it has no clutch material. Use regular oil back there.