I have a rust free 2004 2WD V10 Excursion with 78,000 miles. The truck is stock with these additions; Four new Bilsteins, Roadmaster Active Suspension helper springs, Helwig rear sway bar. The truck has a new set of Michelin load range D tires. The tires were installed by a first rate independent repair shop using state of the art Hunter brand mounting and computer balancing equipment. The work was done by a top flight mechanic with 30+ years of experience. Upon my initial test drive I noticed a vibration starting at 65-70 mph. I took the truck back to have the tires re-balanced. The initial balance on one one wheel was off by half an oz. The rest of the wheels balance / rim straightness checked out perfect. At that point the wheel and tires were declared 'as good as they are going to get'. My slight vibration / thrum persisted. Next we had the drive shaft rebalanced. The vibration improved somewhat but still exists. The shop is out of ideas. The vibration starts around 68 mph. The vibration is coming from the rear. You can feel it in the seat of your pants. The steering wheel is rock steady. I've personally swapped the wheels from rear to front. It did not change the vibration. I will admit that I am sensitive to chassis creaks, groans and vibrations. My wife routinely can't hear or feel things that I complain about. My question is,.... should I just chalk the ride quality up to being a stiffly sprung 3/4 ton truck and not the cushy automobile I daily drive or is there something else that i can / should change or inspect to isolate this admittedly mild but still annoying thrum?

 

No, none of that is normal. I would have the driveshaft checked at a 2nd shop. I had a bad vibration last summer. I had mine rebuilt at what turned out to be a less than stellar shop and the 2nd shop that I took it to rebalanced it and put in quality joints. Problems solved. Axle bearings don't typically vibrate, they tend to rumble more.

 

what type of driveshaft do you have ?

is there a CV joint at he transfer case end or just a single joint ?

must have you vehicles ride heigh to understand your vehicle driveling angle

measure from the center of the wheel hub straight up the bottom of the fender arch.
Post this info for all 4 corners.

also, if you can post a pic of your rear drive shaft, the rear springs, the block between the spring and the axle.