New vibration

[Firetruck]

02 4 wheel drive 1500 Z71
I have always had a slight vibration when towing my bassboat or carrying a bit of a load. This vibration occurs at 40mph and continues to around 55mph. then it disappears. The dealer has checked this and can not find anything abnormal and most of the time they can't feel it. (Of Course)
Now this vibration is evident all the time in the same speed range regardless of load.
Recently had the rear crown & pinion & bearings replaced again for the 3rd time because they were howling. Also have installed 4 new rotors and 2 new U joints plus rebalanced the Michelins again. The vibration has never changed from day one. It is slight and some folks would probably not even notice but it bugs me hard  it is noticable in the steering wheel and in the seat. I have tried to load it down to see if it gets worse but there is no difference. Anyone got any suggestions?? I'm beginning to think it migt be in the Transmission 
Warranty is about to run out..... Would love to fix this but have run out of ideas.

 

[DougD]

Have the tires been road-force balanced?

 

[Firetruck]

Yes
I have tried road force balancing 160.00 beans down the drain

 

[DaytonaZ71]

bad tire perhaps?

 

[ygmn]

Motor mounts?
Tranny mount?
Transfer case mount?
Front axle half shafts?
Bent wheel? or out of round?
Driveshaft out of balance?

Bad shock?

 

[Firetruck]

Well here's an update...
I had a good mechanic check all the mounts, and inspect all hubs shafts etc.
Without changing things he can not find anything that is even suspect.
It's not the torque converter, but may still be a trany problem.
I have re-balanced the tires again and while at the tire store a friend rolled in with his 02 Av, we talked and we decided to swap tires and rims....
Still no change.
Just wondering if anyone has any additional suggestions.....
Thanks

 

[usmarineforlife]

hi i have a 05 av LT

i had the same issue. it took about a 2months to find and fix it. this may save u some time.      It turned out that the transmission had metal shavings from the torque converter. So the dealer ship replaced the trans. U may want to check to see if there is any metal shaving in your trans fluid.

 

[Firetruck]

Thanks
The dealer just performed a flush and Transmission service, nothing has changed after doing that and they have eliminated the torque converter, but I'm not 100% convinced yet.
Latest thing we will try is to take the drive shaft out, send it to a local shop to have it balanced. The dealership says they may need to order a new one.... if it out of balance by a large amount.  We still don't know if this is the cause of the vibration.

 

[Firetruck]

Well now what??

Replaced the drive shaft hoping that it would cure the vibration.
No Change....

I'm really out of options, I guess I will just it drive hard and hope that whatever it is shows itself when something breaks.