I have a 98 XJ with 3" lift and 31s. Changing fluid for 1st time since purchased and not sure what previous owner did. Dana 30 in front and 8.25 in rear. Should I run 75w140 in both the rear and front since lifted with 31 tires? Matter what brand? I've done a lot of searching and couldn't find a real good answer for this so anyone's experience will be much appreciated.

 

I'd run 75w90 unless you live in extremely hot conditions, don't forget an additive if you have a limited slip.

 

Synthetic or Conventional?

 

I might add it is a daily driver and doesn't tow much but might in the future.

 

Cheap and good, and available locally

http://www.autozone.com/greases-and-...oz-/443149_0_0

 

Owners Manual says to use 75w-90 unless towing then use 75w-140 synthetic in the rear axle. API index of GL-5 is indicated. Friction modifier is indicated for axles with Trac-Loc.

My 1998 FSM says 80-90 gear oil for standard use. For heavy duty use/towing 75w-140 synthetic is indicated both front and rear. Again GL-5 and friction modifier if you have LSD.

The recommend interval for changing gear oil is 12,000 miles in heavy duty/towing operations or change immediately after operating vehicle in water above the axles.