Okay, I took a trip down to Dallas Tx yesterday, and found a issue with my van, the 91 B-250, that has me somewhat stumped.
At about 60mph it develops a high pitched viberation that you feel in your feet and seat of the pants, and it goes away after you hit 73-75 mph. I checked the U-Joints, both feel tight, no slop, wiggle, or the like in them. The trans mount did not show signs of slop when I lifted on ithe trans with the jack, and the motor does not torque over showing signs of a bad motor mount . . . . . Did I miss something ? At or above 75 mph, smooth as a van should be at that speed, so I am not sure where to look next.

H E L P !

Tire balance....

Tires would viberate constantly from XX mpg and up, wouldn't it ?

No they generally start about 45 mph

Had one doing that John, turned out to be a caliper causing it.

Thanks guys,

I will go in the AM to the tire shop and get them checked....maybe I threw a weight.

If not that, I will pull the tires off at home and check the calipers for binding on the slide pins, clean and regrease them, and see if that helps at all.....

Beyond that, I don’t know, but I will find it somehow !

Thanks again for the ideas on where to look. I am also gonna give the strut rod bushings a good once over while the front tires are off.

I recently eliminated a similar vibration on my 89 Ford. Van drove fine 0-60ish but had a wicked vibration at about 65-75. Above or below that range it was fine. I took a weekend to address a number of deferred maintenance items, including replacing the u-joints. I had no slop in them and I had kept them well lubricated, but it turned out the front u-joint was too tight and was binding. I put in new u-joints, greased them, and the vibration went away.

If the tires and calipers check out OK, check out the u-joints.

Yep thats another good cause ....

Tires did check out ok, and have not had a chance to check the calipers yet, but replacing the joints is fairly easy and not to expensive, so will add them to the list to do, as preventive maintenance