Off-Throttle Vibration

[mktsc]

Hello, new guy here and searching didn't turn up the answers I sought.

I have an '02 Libby, with just over 100k miles. It just started doing something odd. It will vibrate when you let off the gas. The frequency seems to increase with speed, meaning when I'm on the freeway and let off, it vibrates faster, and when you come to a halt it vibrates at a slower frequency.

There's no play in the driveshaft, but I'm wondering if it could be the front shaft?

Has anyone heard of this happening? It runs and drives fine when you accelerate, and I've tried putting in neutral to isolate the possiblity of it being the transmission or torque converter.

Thanks in advance,

-MK

 

[kj924]

Check your u-joints in the rear....might have a bearing in the rear end starting to go. Start with one end first, then work to the front.

 

[mktsc]

What's the best way to check the u-joints? I checked for play and the driveshaft is solid as a rock.

-MK

 

[kj924]

Take the driveshaft right out out of the yoke, check to see if the caps turn easily on the cross, check to see if the front joint is nice and flexible. Usually, if you get a vibration when letting off the gas, it is usually closer to the transmission end of the shaft.

 

[mktsc]

Thanks for the advice, I'll check it out.

-MK

 

[JeepJeepster]

The front drive shafts do go bad sometimes but you shouldnt be getting a vibration from it since it does not have torque on it unless youre in 4wd. It couldnt care less if youre on the gas or not when youre in 2wd.

U-joints on the rear drive shafts seems like a good place to start. After driving on the free way, feel of the ujoints when you first stop(get home, etc). If they are too hot to touch most likely they are bad.

Another way to check them is to take the rear drive shaft out and see if they move easily.

 

[RenegadeJay]

I thought you were gonna refer to the vibrating at idle. When Iraise the rpms, it goes away. But at a stop, it can vibrate the to the point I see the passenger seat shaking. Wish we had the same problem so I could feel a little better about it.

 

[mktsc]

All vibration goes away when you're on the gas. It's only when you let off the gas and am decelerating. It doesnt matter if the trans is in neutral, or if 4wd is engaged or disengaged.

-MK

 

[kj924]

Chech the rear driveshaft first, sound alot like a u joint to me. The fact the vibe comes when the load is off the driveline is the key.