2002 gmc sierra vibration

my gmc sierra ext.cab has a vibration at 45 on. it can be felt in the steering wheel and the passenger side but not driver seat. i thought it was an axle but i replaced it and still same thing. i had the drive shaft out to change the u-joint. but if it was the driveshaft wouldnt it vibrate the truck??

update: i flipped the driveshaft 180degrees and the vibration is still there!! any ideas??

Check a front tire for a shifted belt?

only at 45? when does it stop and if u go faster then 45 does it also stop?

Is your truck a 4x4? I had a vibration in mine around 50 mph or so, and found that the front drive shaft U-joint was bad. How are your tires?

--Jim

Some wheels do not balance well using the center hole as the shops do.
I've had two cars that needed to be balanced using an adapter for the lug mounting.
Bob B