I just finished a diff fluid change. The truck has 90k miles on it. They look fine to me, but I am no expert.


I do have a slight hum from the rear sometimes. Always from a dead stop, and accelerating... it sometimes hums for 1-2 rotations, till about 8mph. It will also do it more often if I am going up hill from a dead stop to 8mph. I think when I did my pinion seal I didnt put enough pre-load on the pinion bearing.

 

Pics can be deceiving
They could be fine or there could be a major problem around the corner.
They look clean though with out any further inspection

 

Looks like your Clutchpack retaining clip is still intact. It's that w-shaped clip on the inner lip by the spider gear. There are more, but cannot see from just that pic.

 

If all you did was change the seal, don't be concerned with preload. Torque to factory spec and you're good. Your ring gear looks ok. I can't see anything terrible happening. The hum that you hear sounds more like tire noise than gear noise. Are your tires wearing evenly? Check the torque on your yoke nut...

 

That's what I mean, the yoke nut. The yoke nut sets pinion bearing pre load.
Tire noise at 5mph?

 

I saw two of them. Looks like there is probably 4. I couldn't see were the other two would be but they weren't at the bottom of the pumpkin

 

It's not possible to torque to factory pre-load setting with just the driveshaft removed. WHole key here is PRE-LOAD. You must torque pre-load with both axles removed from differential! You get more drag and can overtighten the crush collar if you torque to factory specs with everhtying in place. Then, you'll ned to tear everything apart and start from scratch.
The only thing you can do to make sure the nut is as tight as factory is by marking the nut to the case. It's the only way with the differential together.

Other 2 are on the opposite side of the ring gear.(2 outside, 2 inside)
Check your u-joints for play.

 

If all you're doing is replacing the pinion seal, you don't pull the axles to torque the yoke nut. Nor are you worried about pre-load. After you've run a gear set for a 30+ thousand miles, there is much less pre-load on the pinion than when it was freshly installed new.

I didn't say factory pre-load... I said factory torque for the yoke nut. Two entirely different things.

 

IDK man, every old school mechanic I've ever talked to including the old man (50+ years turning wrenches for a living) says to mark it and replace it exactly how it was.