Harmonic vibration

[Californiafeind]

I was heading down 101 my 92 XLT today. I noticed a slight drown and vibration at about 75 mph. Figured it was the road. Got to Monterey, did the 17 mile drive, got some food, and never went above 45 mph. I did not notice any vibration. I started home on highway 1 and at 65 mph a harmonic vibration started. Proceeding on to 75 mph and the vibration got worse. At 85 mph I thought the dash pop out the vibration was so bad. Is this karma's way to keep my at the 65 or what? Please help as this is my daily driver.

 

[MAXIMIS1]

have your shocks checked or check them yourself. get the front or rear both eventually , bouncing real good , then let it go, and it should not bounce more then once. twice is acceptable. then look into tire ballance and or seporation, sometimes rotating them will give you a better idea of its orgin if not eleminating them from diagnosis.

 

[Positive Vibes]

When was the last time you got your tires rotated and balanced?

My '94 had a harmonic balancer on the rear diff. I took mine off and couldn't tell the difference. Not sure if a '92 had that?

 

[Californiafeind]

About 2 months ago.

 

[sn0border88]

ball joints, wheel bearings and u-joints could all be the problem. Id start by replacing the rear driveshafts u-joint.

 

[Robot Lincoln]

I'm having the same problem, though the vibration is now starting to occur at 45MPH
This thread helped me by the way:
http://www.explorerforum.com/forums/showthread.php?t=14540&highlight=vibration+MPH

 

[Rhett]

In these trucks the radius arm bushings will cause a 65-72 mph vibration if they are bad.

Given that your vibe is 65 all the way up to 85+ mph, you quite possibly have multiple things wrong with your truck: RAB's, bearings, u-joints, etc. I'd start with the radius arm bushings and go from there.

 

[Californiafeind]

It's fixed. The U-joints were seized up.

 

[Robot Lincoln]

Solved

It turns out that the problem was in the mounting bolts on my front driveshaft; three had come loose and one was missing. The bolt is not a standard part, however, and must be ordered from Ford.