Drive Train issue Question

[ScottATL]

Hey, new here.
110,000miles
Have a shudder in my drive train someplace. I have had 12 mechanics look at it and everyone has different opinions as what it is including the dealership.

The truck started shuddering barely(enough that you know something is wrong, but someone borrowing might not) from 20-45 mph, definately noticable under load towing a 2k trailer going up a high. Another issue that I have had was I could engage 4wd high, but going back into 2wd high was an issue, would take a couple blocks to get it to finally pop back out.

I have had opinions from cv axles to front dif to transfer case to ujoints to rear diff.

Sat I had the mechanic replace the 3 ujoints in the rear, the carrier bearing and the transmission mount.

Upon completion the shudder got 100xs worse, it starts at 20mph, gets worse until high 40's and lessens above 50. this is with no load.

various other opinions after this.

So, this morning I had the mechanic remove the rear drive shaft and then we covered the transfer case and took it for a drive in 4wd high, smooth driving. once we put it in park we shifted the 4wd back to high and put it in gear and it changed w/o an issue.

Question is: does this completely rule out the transfer case and the rear Diff(since it was spinning while driving)

I'm having him take the drive shaft to a specialty shop to have it balanced and to check that the parts he put in Sat were good.

Since everyone including the dealership seemed unsure and bounced around, I figured I would lay it out here and see if anyone has dealt with this.

Thanks,
Scott

 

[Harley Harrold]

 

[Joe.G]

Start with the Drive shaft, Make sure it is balanced and straight, Make sure the U Joints were put in right pressed in not beat in. put the D Shaft in and try it, if it still feels a bit off take shaft out and spin it a half turn and put it back in some shafts like to be in a certain position that's why I always mark mine before removal.

If that is not the issue check it on a lift Is the tranny smooth just the rear feel odd while it is up in the air.

 

[MADDOG]

Several things come to mind:

If you've serviced the transmission then I'd rule out needing fluid.

I suspect the torque converter, pump or valve body may be the issue.

Has any of those 11 or 12 outfits suggested getting into the transmission?

How are the shifts? Firm and positive or slow and slippy?