hey guys so i had to drive 100 miles to work for a week then drove back and on the way back i noticed a very fast vibration and it would stop if i let off the gas and just coasted? i just put brand new tires on so i know its not the tires or lugs. but its weird that it only does it when im accelerating. i thought it would be just the driveline bolts were loose. but i tightened all those and its still doing it! please help.

 

does it only do it when youre moving or when you are sitting still too?

 

Sounds like a worn U-joint to me. They usually start to vibrate when just on the gas or just off the gas when they start to go bad. The other and more expensive thing would be rear diff gears but, I'm leaning more toward a U-joint.

 

I'd also lean towards u-joints being the cause. Get under it and check for any play. Have an assistant rock the tire in a jerking motion(forward & back) while you watch the joints carefully. It doesn't take much wear to throw them out of balance. If so, replace before failure occurs.

 

just when im moving and it is only when im going 40+

 

but there is no play in the driveline. could it still be the u joints

 

ok and when i rock the tires back and forth the joints are tight but there is play inside the rear diff and its making a clunking noise!!

 

does that mean something is wrong in the diff?

 

grease everything, dry d/s ujoints can vibrate. do you notice it more in the front or the rear?

 

How many miles does your rear diff have on it? If it's less than 200K and you can live with the vibes, I'd make sure the axle gear oil is full, grease your U-joints and let it go. You don't want to have to rip into that diff. prematurely unless you're doing a gear swap or it's just eating itself alive. Very expensive!

 

letting off the gas indicates UJOINT..get under your jeep and shake the rear drive shaft.. if i moves up and down.. look at the cups on the ujoint shaking or moving without the yoke moving.

mark

 

the jeep has 120,000 on it so it shouldn't be the diff right? but i'll check the fluid and grease it up and see what happens.

 

yeah definitely i'm leaning toward u joints