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70 MPH Vibration

Here is the deal. I have a 1990 Astro van clunker but can’t aford to trade it in on a new car. It has a vibration at about 60-70 mph. I have searched everywhere on the car for the sourse of the vibration and can’t find it. The tires are balanced, tie rod ends are OK, and the U joints are OK, the front brakes are fine and the calipers are not warped. What else could it be? It has 120K miles and is in good condition, never wrecked. Roger

If you swap the wheels/tires front to rear, does anything change?

Did that last week. put new on the front. Nothing changed.
Roger

The next suspect would be a drive shaft that is bent or out of balance. Is there any evidence that it has been abused?

I remember when I was a kid that on some cars I worked on, the drive shaft was balanced as a unit, so if you took it apart to replace a U-joint, you had to mark the sections and assemble it just as it came apart to keep it in balance. I don’t know if this would be the case on your van. Any chance of finding a good driveshaft cheap at the junk yard?

Good idea. Can you balance drive shafts? Wonder what a used one would cost? Roger

You can (or, preferably, buy a used one), but first thing to check is the u-joints, one may be going bad.

I had the U joints checked when I put the 2 front tires on. They were OK??. Roger

Also give the motor/trans mounts a good once over, though I’d expect problems there to show at lower speeds too.

I do recall a really long thread on here once about a van vibration that actually turned out to be from out of round rear brake drums.

Just spoke with my mechanic. He is going to pull the drive shaft next week and check for balance and dry bearings. He is also going to check th motor mounts.
Thanks, Roger