vibration at 50 to 65 mph?
 

Had a vibration in the rear when i bought it came home a switch out wheels and tires and lowered 4/6. had it aligned and pinion angle check and i have the same vibration any ideas and ways to check possible driveshaft. Truck is a rcsb 2004 gmc with 50k. vibration is not in the steering wheel it is the whole truck. ie seats floorboard

thanks

it's doing the exact same thing for me. I can drive 125 with zero vibration but 50-65 has a ton. I'm lowered 3/4 with control arms and hotchkis leaf springs

You say your pinion angle was 'checked' but what is the angle? :confused:

Also, knowing the pinion angle without knowing the transmission output angle means you have incomplete information. You need to have both angles to make a determination if things are okay or not.

My angles were equal with a 2* shim but because of the torque I needed a 4* shim to compensate.

I understand the angle but it shoke the same before it was lowered?

You should have cured the shake before you lowered it. IMO.

Jim

i know this is almost too simple, but I have found mph specific vibrations almost always end up being a balance issue. Yeah, tire. You may have already checked, but make sure those rear tires are up to snuff before you waste alot of energy and money chasing this. And CHEVY6000VHO has a valid point, the same point everybody learns the hard way, don't mod more if you have issues with something else.

What kind of wheels did you switch out to?
Did you remove the assembly line brake rotor clips that have two on each hub/ stud assembly? You will see them on two of the studs when you remove the wheels. These will not work with most aftermarket rims. They cause the wheel not to sit flush against the hub.
Just a thought that you may have over looked.

Jim

If the vibration began after lowering the vehicle, and the tires are properly balanced, you probably need to shim the rear to correct the pinion angle. Funny thing, I used to have a similar vibration (about 55-65 mph) before I lowered my truck. It happened since day one, with the factory Firestone's and with my larger BFG 285's (33"). Ever since I lowered my truck, it has been smooth as butter...almost makes me think I had a factory pinion angle or driveshaft/u-joint problem that was corrected by lowering.

:cry: Hey check out my post I have a 2003 and have the same problems it will not be your tires or your drive shaft. I did this and changed two drive shafts due to the other one breaking out. :cry: because of the vibration. It will not get better only worse. :cry: I lowered mine and the pinion is off check out the links that I have been told to go to. Let me know what you think. :confused: