Rear differential oil suggestion and possible pinion leak.

[WDE86]

1. What kind of gear oil are some of you guys running? I've always had luck with Royal Purple synthetic motor oil and I'm leaning towards using that (75w-90), but I have no clue clue what's best honestly.

2. I know I have a leak at the rear differential but I'm having trouble determining if it is simply my cover (a 10-bolt) or the pinion. I do not have a trail coming from the front of the drive-shaft to the bottom of the diff. but is that a clear cut way of knowing the pinion isn't leaking a little? Or maybe the pinion leaks only when I am driving but not when I am stopped?

[CBot]

if you have a pinion leak you will have that trail and you will have diff fluid slung all over the bottom floor of your bed. one way to know for sure is make sure your differential is topped off with fluid. dirve the truck a good ways then check for that trail. I used valvoline 75w90 on my last diff fluid change. make sure to check the pinion bearing by shaking the drive shaft and see if it moves up down side to side any in the differential.

Originally Posted by WDE86

1. What kind of gear oil are some of you guys running? I've always had luck with Royal Purple synthetic motor oil and I'm leaning towards using that (75w-90), but I have no clue clue what's best honestly.

2. I know I have a leak at the rear differential but I'm having trouble determining if it is simply my cover (a 10-bolt) or the pinion. I do not have a trail coming from the front of the drive-shaft to the bottom of the diff. but is that a clear cut way of knowing the pinion isn't leaking a little? Or maybe the pinion leaks only when I am driving but not when I am stopped?