Front and rear diff basic questions

[dcorwin822]

how do i know if i need to add a friction modifier? Its a stock truck.

I'm also going to assume i need 80w90 for the front and 74w140 in the rear.

do i have to remove the housing covers to completely drain the old junk out? anyone have a how-to?

 

[Thelt]

I just have this done at the shop but I do not think you need the friction modifier unless you have the limited slip differential.

 

[EXPLORER04]

front - 80w-90
rear - 75w-140

does not need any additives

draining: the rear has a drain plug in the bottom so just open let it drain for a while then refill. The front does not have a drain plug so you can either use a suction pump or pop off the cover. hope this helps