I'm a newby to the site, but I have a 1999 dakota that has a very odd problem. First off the truck is a 99 w/ a 3.9, 90k miles, 2wd and a manual tranny. The problem is that I have a odd vibration when the car coasts down to around 8-15 mph and it starts making a rubbing/vibration that can be felt through the bottom of the car and seat. Now I know most will say rotors and it is not the rotors because the vibration is not coming from the steering wheel or front end. What I have replaced so far...New u joints, new calipers, pads+rotors, hubs,bolts in rear endand I checked the tires and back drums they are all fine. Let me describe to you the problem in a little more depth...If i slow the car down(coasting or braking) the car around 8-15mph will make a awful rubbing/vibration(has to be rotating assembly becausethevibration is felt as the things move)that can be felt through the seat and backside of the truck(also can be heard on outside of vehicle). Here is the very strange part, I can accelerate to these speeds nothing, I can accelerate to 15mph then let off and there is nothing. The only time it will make the noise is when I go above 25+ then slow back down and it will do it everytime. I do not believe it has anything to do with the tranny because with a vibration this nasty I think I would feel it in the shifter and I do not. I am truly stumped and the only other thing I can think of his the harmonic balancer, checking weights on driveshaft(does not look to be missing any weight).
Can anyone throw out any ideas? Any similar problems?

 

I would check the rear axal.

 

The rear axle slipped my mind, I think I will take a look at it tonight.