I am getting a vibration on the highway. It only seems to happen when I am off the gas. For example if I am driving at 70-75mph and I let off the gas a slight vibration develops. This usually happens when I began to go down a hill. I will let off the gas but keep my speed the same. The vibration starts as soon as I let off the gas. When I reach the bottom of the hill I reapply the gas and the vibration goes away. The vibration is minor but it is there.

Does this sound like a u-joint is starting to go? If so how do I inspect them? How many are there and which ones are most known for having problems?

BTW, I have a 1999 SC 4x4 with 157,000 miles. I recently replaced all the ball joints, tie rods, shocks, idler arm, rotors and pads. The problem I described is when I am in 2wd. I know that may be obvious since 4wd isn't needed at 70 mph but I figured I should mention it. Also, I know the problem is not wheel balance related.

 

I have a 1997 xl supercab 4x4 and i have the same thing start recently as well i am almost positive that it is ujoints i have bought all of them to replace them but i haven't gotten around to changing them ... but i know for sure i have atleast one going. I will try and get to them tonight and let you know if it goes away . Pretty sure it will

 

Hello beekermartin,
Do you feel the vibration when you are backing up? Have you tried backing up for 100' or so just to listen for or feel for the vibration. This really does sound like a u-joint problem from your post. Does the vibration happen at lower speeds when you let off the gas, like 30-40 mph? You can check for overheating of a bad u-joint after driving by feeling the joints. Be careful as if you find a bad u-joint using this method it may be VERY HOT! Touching it and holding it is not a good idea. Do you have a carrier bearing in the driveline?
You can also check the transmission mount with a large pry bar lifting the tailshaft by the mount to see if the bolts or rubber are broken or loose. Just a couple of thoughts...Joe

 

Quite often you can't feel a bad u-joint without removing the driveshaft.
If you remove it you'll be able to move the u-joint through it's range of motion and feel for any binding or looseness. Seized u-joints will feel often good with the shaft in the truck.