Ok, I posted this a while, and tried a few things, and see seeing it - just not as badly...

When driving on a smooth freeway / roadway, if I get to about 70-75 MPH (legal in my area, on these streets), I feel what can only be described as a high frequency vibration in the steering wheel / floor boards, accompanied by a low hum.

I have checked my wheel bearings - they seemed fine, and were packed well, but a little loose - so I snugged them up to take out the slack, and there is now no vertical play in either front wheel.

I have also removed the inner fender slash sheilds, as someone mentioned they had the same problem, and this fixed their's (mine were horribly torn apart by a previous heavy-handed shade-tree, in an attempt to get to the shocks) - to no avail.

The ONLY play I find in the front end APPEARS to be the passenger side INNER tie-rod end, and it's not much.

Also, just discovered yesterday, while cruising on this same road, with cruise set to 65 (to avoid the vibe and hum), I noticed that when I crossed an overpass, and on the downhill drop from it, the vibe and hum returned, even at the lower speed - but was no present when driving on level ground, or uphill - and only seemed to be while in cruise - so perhaps something related to decelleration.

Any ideas on what to check?

I can, and will replace the wheel bearings, if deemed needed. Rotors too, if neccessary. Already planning to replace ALL 4 tie-rod ends, to be safe.

Remember, currently, there is no vertical play at all on either of the two front wheels, which suggests the ball-joints and control arm bushings are still in OK shape...

Oh, this is on a '91 2WD ext cab with the 318...

 

Check out the 95 service manual we have in the FAQ. Go to section 22. It give a complete diagnostic of vibrations. A nice chart on speed of vibrations.