Yes, I'm going to do it and add to the many many vibration threads we have in here. I did my 'search' and it seems that most of the vibration threads have the person stating that a vibration in the steering wheel can be felt at "X" MPH (usually above 55 MPH). So in reading a few of threads that sounded related my problem, I haven't found a thread that sounds like my concern: a speed-sensitive vibration; meaning that I can hear and feel a vibration (seems like the front-end) continuously - it just depends on the speed of the vehicle.

Here is a simple, and hopefully logical, explanation of what is occurring:

At slow speeds, under 10 MPH, the vibration sounds like this: "rumf.....rumf.....rumf.....rumf.....rumf.....rumf "

As the speed increases, the intervals between the vibrations decrease:
"rumpf...rumf...rumpf...rumf...rumf...rumf"

At highway speeds, let's say 60 MPH, the vibration is practically constant:
"rumf.rumf.rumf.rumf.rumf.rumf."

Hopefully the word "rumf" is logical enough. It seems that its like one part of the tire has a bad spot or something and everytime the wheel rotates to that one spot I feel the vibration and hear the tire noise. And, even as I decelerate (coasting), the vibration lessens as the vehicle slows down. I'm thinking it's a balance issue but I wanted to get some other opinions before I take it anywhere. (I'm a college student attempting to save where I can)

Tom

 

Could be the driveshaft u-joints. Is there a change in the sound if you're in 2H versus 4WDH?

 

Haven't played much in 4wd. I will give that a try later on and report back. Thanks for the idea, I will try it.

 

The 97 & 98 model years came with a Double Cardinal U-Joints (front of rear drive shaft) which is 2 Universal Joints with a centering pin and what happens is the centering pin wears and will cause a vibration, I had a 97 expy that had this problem and ended up replacing the rear drive shaft from Ford ($200) and due to the vibration it also wore the bushing in the tail shaft housing in the transfer case ( were your yoke slides into transfer case ). BTW the replacement drive shaft was new style with single U-joint not double cardinal, so I think FORD was aware of this problem

 

how are your tires? are they wearing evenly? cupped ?that can cause vibration and noise. you can rotate the tires and see if the sound moves.

 

How can I check this pin? Should it be loose or should it have some form of visual wear that I can see?

 

The pin is hard to see without disassembling so the best way is to see if there is play between the two U-joints or remove drive shaft and take to a shop who rebuilds and balances drive shafts I took mine to a shop that does heavy truck drive lines and they informed me at the time (2003) that parts were not available to rebuild so that's why I ended up purchasing a drive shaft from Ford.

 

The tires are Goodyear Wrangler RT/S. They aren't bad although tread is becoming shallow...but it's not like I'm running slicks. I went outside to do the 'penny check' on the tires and with a quick check on the tape measure revealed my tires have just under a 1/4" on tread left. Tomorrow I will go out and do a better visual check on the tires during the day time. In addition, I will check the DOT specs on it to see what year they were manufactured. There's a possibility they are at the end of their life. Maybe this will be my excuse to purchase the All Terrains I've been wanting.

 

i was looking more towards cupping run your hand across your tire from front to back, then back to front, see if your hand cathes on the tread. tires can really mess up a nice ride. i had cupped factory continentals on mine. i put some michelins on and it is smooth. you actually may be able to see the wear from a distance. some tread blocks will be a different shade than the others.


not saying this is the answer but it is a simple start.

 

Drive down the highway to where you get the rumf, rumf.rumf sound, THEN take it out of gear and coast. IF the sound is still there it is a good chance it is NOT the U Joints. Another way, block the wheels and take it out of gear, get under it and try to move the drive shaft back and forth, if it moves a lot its the U Joints. I would also check the wheel bearings.