2005 Tahoe/Rear end rumble after new seal?

[88lance]

'05 Tahoe 2wd, 5.3. ran smooth as glass down the road, no sounds, no vibration.
Noticed rear pinion seal was dripping. Took it to a mechanic shop because I don't have time to mess with it.
He replaced seal, good to go ... Took it on the road, and at 55+ mph, it starts making this bad grumbling sound in the rear, and slight vibration.
First thought "they didn't reset the ring and pinion correctly".
They took it apart on the back of the housing, and checked adjustment, "it's sitting properly, nothing wrong".
Went to another shop, told them what's happening, they suspected the same thing. Took the cover off the rear "nope, it's actually adjusted correctly, there is nothing wrong in there, so you should probably replace U-joints"
Did that, nothing changed
Back to another mechanic shop, they put it on a lift and run it up to 70mph. Notice that the drivers side wheel kind of shakes at 70, like the bearing is out or something.
(Why a bearing would decide to go out the moment I replaced a pinion seal makes no sense, sounds doubtful, worth a look though).
They take the driver's side out and bearing and all inside components on the end looks new, no marks, no wear from something being out of line, nothing.
I'm stumped. I would really lean towards something being wrong with the rear gear set since this began the moment they replaced that pinion seal, but now a total of 3 mechanics have checked the adjustments on the rear gears and said it is sitting exactly where it should be.

I did consider whether it was the right type of fluid if this was a limited slip, but I checked and it's not limited slip though.
Not sure what to think from here. Anybody know more about these or encountered something similar?

 

[swathdiver]

Do you know how the process works to replace a pinion seal? Do you know exactly what kind of fluid was put in this by each of the three mechanics?

Right before the pinion nut was removed to replace the seal, the mechanic would have taken a measurement with a torque wrench to see how many inch pounds of torque it takes to rotate the pinion. After replacing the seal and new nut, they then add 3-5 inch pounds to the previous number to maintain the pressure on the crush washer. Scribing a line on the old pinion nut and then torquing it back to that mark is not proper despite all the youtube videos.

It is far from a coincidence for more than one thing to break at a time, especially when it is in the shop. I ran some shops over the years and we were blamed for stuff all the time.

You have a 19 year old car now with so many miles, bearings don't last forever. Might need new axle bearings, differential bearings, etc.

You are doing the right thing but ask about that rotating torque before and after numbers and especially the fluid used.

 

[88lance]

Do you know how the process works to replace a pinion seal? Do you know exactly what kind of fluid was put in this by each of the three mechanics?

Right before the pinion nut was removed to replace the seal, the mechanic would have taken a measurement with a torque wrench to see how many inch pounds of torque it takes to rotate the pinion. After replacing the seal and new nut, they then add 3-5 inch pounds to the previous number to maintain the pressure on the crush washer. Scribing a line on the old pinion nut and then torquing it back to that mark is not proper despite all the youtube videos.

It is far from a coincidence for more than one thing to break at a time, especially when it is in the shop. I ran some shops over the years and we were blamed for stuff all the time.

You have a 19 year old car now with so many miles, bearings don't last forever. Might need new axle bearings, differential bearings, etc.

You are doing the right thing but ask about that rotating torque before and after numbers and especially the fluid used.

Thanks for the response. I knew the pinion nut was the adjustment, I assumed they would probably know that as well. Which they say they did when I asked them about it after the issue.
I'm not sure what type of fluid was put in, I just checked to see if it was an open rear end or limited slip, in case it needed to have that certain fluid for limited. I'll see if I can figure out what they filled it with.
If they do not know what the torque was, or if a different mechanic is messing with it next, I guess they will just need to look at how the gear is sitting and make adjustments and see what affect it has?
I was curious if messing with the ring and pinion while replacing the seal could have unadjusted some bearings and caused it to start having trouble, which is what needs replaced now possibly?
The bearings at the end of the axle look really good according to him, but if there is another set near the gears on the inside, that maybe the whole problem.

 

[nonickatall]

Did you check the needle bearings of the Drive shaft? Sometime needles fall out, than you can get unbalance, which can cause wobble. Yes, that should not only impact the driver side, but sometimes vibrations take strange ways.

But as well you can have a failed wheel bearing or it may also be that you have lost balance weights on the tire. Sometimes you have correlation, without causation. Try change the tires from left to right, to see if the problem moves to the right.