Weird Vibration... Driveshaft / U-Joint or Motor Mounts?

[domoarigato]

Hey guys,

I've been chasing this weird vibration I'm having. I've searched for possible symptoms, but it doesn't really align with anything specific. 2011 tahoe with 170k, 2wd.

I will get the tires-re balanced to rule that possibility out but I've gotten them balanced before.

Symptoms:

- Sometimes low speed vibration, happens more often when I'm on a slope.
- Quick vibrations on the freeway 65mph+, feels like its coming from below. Goes away when I give it gas.

I was initially thinking driveshaft / u-joints because the vibration stops when I put load on the drivetrain. However, I'm not experiencing any weird clunking noises.

Any ideas as to what it can be? I dont want to blindly throw parts at it, but at this point I may have to.

Thanks.

 

[kbuskill]

Apply the parking brake and hold your foot on the brake and put the truck in drive and give it a little throttle while letting someone watch the engine to see if it torques over.... repeat the process with the truck in reverse.