I've picked up a vibration which starts at ~ 78mph and which then stops at ~ 82mph. Below or above this range the vibration is gone.

Does not appear to be engine related as I can let off the throttle or even shift to neutral and the vibration stays the same - until the truck coasts down to below 78mph.

Any ideas or suggestions to troubleshoot this would be appreciated.

Mark

Have the tires rebalanced.

If that doesn't cured it, check the driveshaft for weights knocked off. Could also be the carrier bearing if 95s have one.

Where do you live, Montana? <img src="/forums/images/graemlins/lol.gif" alt="" />

Yep, sounds like a drivetrain vibration. rebalancing might help, although most balancers will not simulate that kind of speed. A Hunter Road Force rebalance probably is your best bet. You can check the Hunter site for a machine near you.

I have balanced and rotated the tires with no notable change in the vibrartion.

The truck also has a bit of pulsation in the brakes like possibly a warped rotor. I'm wondering if there could be a possibility of the two issues being related as they both seem to be worse on the right front.

Do the rotors seem a possibility? I started chasing the vibration by changing the rear u joints which were shot but did nothing to change the vibration.

Mark

I was going to say the same thing about having the tires re-balanced. Ok another thing to keep in mind is that they are not a high speed tire and as speed is increased the overall tire is streching and becomes uneven, resulting in your vibration problem, at those speeds I have vibration but my tires are zero'd on my balancer which also happens to be a Hunter with road force feature, even with the road force they all stayed well below 15 LBS which is great for an aggessive tire. not a bad machine for 25,000$ AHAHAHA. also get your front end checked out also, sometimes vibration is not the result of tires but front end work needs to be done. By the way I work at a tire shop (Big O), so I can help out in those area's HAHA

The strange thing though is that just as the vibration starts at 78mph (indicated - the tires are taller than stock) it also stops right at 82mph - above that it is smooth.

The tire wear is also very uniform. I've tightened the steering box and all the rest of the front end has no slop that I can find.

In my testing today I'm questioning my thoughts on the rotor. If I apply the brake (just a tiny bit) and it was a warped rotor it seems the vibration would change (for better or worse) but it does not change. I can also feel the vibration come and go more in the transfer case lever than I can in the steering wheel.

So I'm back to wondering about the balance of the drive shaft and/or the possiblility of the front U Joints being bad. The drive shaft was put back together the same way it came apart but the U joints are different - the new ones have the zerks at the ends of the caps where the old ones had the zerks at the base of the joint.

Could the placement of the zerks be enough to make the driveshaft out of balance?