Happy New Year!
My 04 Suburban has a vibration that has torn out 2 rear ends so far. Just turned 200,000 miles. Even though I've wasted thousands so far, I love the vehicle itself & want to FIX it somehow. I'm more than willing to pay a local welding shop to add extra supports if needed, or buy different diameter tires/rims, or whatever it might take: I'd just like to know WHAT it needs.

With over 10 years of GM'* vibration problems, I'm hoping SOMEBODY understands what is occurring & what might be done to fix it.

Any help would be GREATLY appreciated.

Initial vibration was only noticeable at 73 MPH (started at 71; gone by 75) Whether in gear driving or coasting downhill in neutral with tach at idle. Same in 2 or 4 wheel drive
Since rear end replacement now at slower speeds 30'* & 40'* also
Cruising at 67 is still smooth as a rail (at least for now)
500lbs at back of cargo area slightly helped the 73MPH, but worsened the lower speeds.

Just my own wonderings:
1. Rims & Tires weigh more than they used to; creating different weight distributions compared to the rear end. I'm told Ford adds "tuning" weights to their rear end housings, but haven't heard exactly why or how to.

2 Maybe use 15" rims like these vehicles had in the old days before vibrations issues began......

3. This has a transmission mount under the transmission, but the transfer case just hangs in midair. Seems like a whole lot of weight not be be supported anywhere aside from being bolted to the transmission.

4. Possibly add a support &/or carrier bearing to the back of the transfer case?

Vehicle History
Even mix of local & interstate driving.
04 Suburban LT 5.3 3.43 rear end 265/70R17 Tires
No accidents/damage of any kind
Rebalance Tires
Replaced tires
New Rear Shocks
Balanced Driveshaft locally
New U-Joints on Rear driveshaft shaft both Front & Rear
Replaced entire rear end housing, pig, axles, bearings, rotors, brakes
Rechecked balance of driveshaft at specialty shop correcting a small bow .055" out of round

Drive shaft universal joints

Great call 1.8TTony. THANKS

Found a bend "clamp" that holds the u-joint cap into the pinion mount.
It was letting one of the u-joint caps slide forward ~.025"

I'll get a new one & report back.
Can't believe the last 2 mechanics missed this.