Vibration At Specific Speed?

[LuxuriesPremier]

Hey guys i am kinda stumped on a problem i am having with my 2000 GMC sierra 1500 4x4 ext. cab. When the truck reaches 80 MPH at the line i get a heavy vibration i feel in the floor of the truck and as i increase speed it stays until 85. When i go over 85 all the vibrations disapear completely.. I rarely drive at that speed but its annoying if i do. My only guess is possibly an overdrive kicking in and/or torque converter issue ?

[Cool Zr2]

Could be you lost a wheel weight and it is off balance, slightly bent rim, bad u joints.....

 

It could be a bunch of things, bring your truck in for a balance/rotate and ask them to check the u joints.... The balance/rotate will find out if one of the rims might be bent or tire off balance.....

[saltwater_addict]

happens everytime my tires hit about 50000k, not horrible for mud tires though although its usually at about 45-55mph.

[ewiski]

I had a vibration in my steering wheel.I had my wheels balanced about 5 times.After complaining the last time they finally found one of the tires had a bad belt.

[Wingnut]

Every time I've had a vibration at very specific speeds (none above or below a specific range), it's been the ujoints.

[CapitalTruck]

U joints could be a culprit. If not U joints, it could be a "bent" driveshaft. By bent I mean slightly out of specifications. I had a 1987 G Van that had the same problem. Took it to a shop that flushed my money down the toilet. Took it to another place, guy drove it, within 2 minutes "oh yeah, feels like your driveshaft is out of true". Went to a spring shop nearby, they put in a new driveshaft, viola, rode perfectly. So, if you rule out your tires, try your Ujoints. If that doesn't do it, probably the driveshaft.