can i safely run 80-90 in my rear diff?

 

yes

 

just put some in mine a week ago

 

Alright just wanted to make sure. My front is 75w-80 tho. Does that matter?

 

What do you mean your front is 75w-80? That weight of lube should only be used in very cold climates in that Dana 30 front. A 75w-90 or the 80w-90 weight you put in the rear axle would be ideal for most applications. Good ol Valvoline 75w-90 and 80w90 gear oil and even 85w-140 for the rear axle if towing, meets the most requirements for a affordable, conventional oil.

 

I run 75w-110 front and rear. You can use 75w/80w-90, 110 in both.

 

Sorry I meant 75w-90 in my dana 30 front. I found two bottles of 75w-90 for the rear so I'm set now.

 

Haynes manual says to put in a couple ounces of "friction modifier" as well, I found some at napa

 

Only required if you have a factory limited slip.

If it's a stock open rear, no additive is required.

 

how do i know if its an open rear or not?

 

Lift the back end up and spin a tire. If one spins one way and the other spins the other way its open.

 

mine would be open. thanks!