Vibration---help!!
 

I have been dealing with a vibration in the steering wheel for a couple months now. It only does it between 40-55 mph and is only really noticable under acceleration not when at a constant speed. I had my tires rotated and balanced, but it did not change--any ideas?

http://community.webshots.com/album/28312904DvrHcOvZDy

Idler arm, wheel bearings, alignment, out of round tires or rims, bum u-joints in the driveshaft, bearings going in tranny or t-case output, over or underlubed drive shaft.

Lots of possibilities, what all have you checked besides the tires?

I have been under the truck on a lift to visually inspect things. Nothing seems loose, bent, or out of place.

Under power 'eh?
One more bone to throw in the mix, broken/loose motor mount?

Does the rear propeller shaft line up correctly? It happened to me before on my older '89 4Runners (lifted) when the shaft got separated after rear axle dropped down too far. I put the shaft back together, and forgot to check the lining up the joints at both end of shaft. I got a wired vibration under the acceleration for a while. Until, I realized that was a shaft, so I had to correct it. The vibration went away.