I'm trying to figure out where a vibration is coming from in my truck. I got new tires about a week and a half ago. After I got them I could feel after a few days they weren't balanced enough. Took the truck back and they re-did them. Everything was fine for a couple days.
Now I'm getting a vibration from about 70-100 km's that is only happening when I'm on the gas. If I let off and apply no throttle, the vibration goes away. At first I thought it could be a u-joint... but it would be the opposite of the way things were happening with that. Also inspected those and they seem fine.

I think if it was the tires being un-balaced still it would still vibrate even if I let off the gas.
Could it be the transmission?

 

Do you have a 2 peice rear drive shaft? Could be the hanger bearing if you do.

 

No it's a one part shaft. I just took the truck for another drive. I can notice the vib even at lower speeds now. And again.... as soon as I let off the throttle it's gone.