I have a 1995 ram van that has a weird vibration to it. It's not the tires (had those balanced). It only does it if you're going between about 45 and 70 MPH - any slower or faster, and it's not noticeable. The weird thing is that when you let off the gas or put it in neutral, the vibration goes away (another reason it's not the tires). The only other thing I can think of is the universal joints. Do you guys think they're a possible cause of the vibrations?

 

Yes u-joints can cause vibration, but it will not go away when you let off the gas. Your vibration is tied to engine RPMs not vehicle speed, I'd say you have a minor skip in the engine.

 

No, it's tied to vehocle speed. When I'm going about 45, I can feel it with the trans in 3rd (engine RPM on the lower side), then I can put it in 2nd (engine RPM much higher) and get the same vibration. Thats why it's so strange - it seems like it would be the engine, but it's couldn't be because of this. I also don't think it's the U-joints anymore, because they're not loose.Also, after running 60 MPH for a couple minutes and then feeling them, they're not even warm.

 

Based on your last description I see three possible culprits. The output bearing of the tranny is worn, the pinion bearing on the differential is worn, orthe driveshaft is bent or just out of balance.

Alternately, one of your rims could be warped or a cord broke in one of the tires. But in either of these cases you would feel the van or the steering wheel wobble rhythmically side to side at low speeds more than at high speeds.