I have a vibration as my speed gets above 50 mph. My 2001 Excursion sat 1 year and I had the dreaded oil pan rust out and subsequent dealer replacement. Ouch$. Additionally, my rear diff cover rusted out and I had the cover and fluid replaced. With all this work done, I have a vibration that comes on going from 45-50 mph. 2WD or 4WD. If I let up on the throttle and coast it isn't there. Only when I power on. It has 144K miles and original CV joints and driveshaft(s). I'm not sure whether it's the CV joints (no strange noises) or drive shaft(s). Tires are fine too. Any way to pin it down?

 

Time to crawl under and start looking. I had a vibration in my front end that would come and go. At times it would get really bad, and then just go away. Turned out to be a seized brake caliper pin. Changed it out last week and it's been fine since. But, due to the fact that your vibration goes away when you let up on the throttle, I'd be looking at the driveline.

 

Thanks for replying JEV. I did in fact go through all the brakes too. All caliper brake pins. One was so bad (seized in the caliper frame) I had to replace the frame. The vibration is still there. I've read that how the drive shaft is bolted on (orientation) can be important so I'll look at that next - unbolt turn and rebolt.

 

If related to corrosion as it seems, I would think it could be the U-joints in the driveline. Easiest thing to do is to remove driveshaft, take it to a driveline shop and have new greasable Spicer u-joints installed and then balance entire driveshaft assembly.