In article <vSK4u.36738$K71....@fx21.iad>, "Snag" <
snag...@msn.com>
wrote:
From what you said I suspect it's wheel related. Out of balance tires
often act up within certain speed 'bands'.
If wheel speed vibration frequency sounds right, look for loose lugs and
missing wheel weights (there will usually be a dirt 'witness mark' on
the rim where a lost weight was). Look at both sides, inside and out.
Look over the wheels/tires for obvious things like ply separations, wads
of stuck on spooge or whatnot.
A bad front wheel bearing/s can sometimes produce vibrations that vary
with vehicle speed... and as they get worse can even induce an eerie low
pitch 'humming' like sound into the vehicle. I haven't run into many of
these, but the ones I have were more felt than heard, and sometimes
seemingly originate from 'everywhere'.
If after all the driveshaft is suspected, go under shake/wiggle as
mentioned above looking for joint slop. (RWD driveshafts rotate much
faster than wheels, so if responsible, the frequency will be a good bit
faster.)
If you can quickly (and safely) dash under the truck immediately after
driving, feel for hot bearing cups. Use caution, a bad one might be
quite hot.
If so equipped, look at the shaft center support & bearing... check it
for mounting security and bearing slop.
Look over the shaft itself for stuck on spooge, foreign matter like
rope, extension cord or the like wrapped around, missing bolts, physical
damage etc.
Also, some vehicles have a fair sized weight bolted to the transmission
output shaft housing to 'soak up' vibration. If you have one, be sure
it's tight. While there, grab the output housing or front of the drive
shaft, shake and check for a busted or sloppy rear engine mount.
Not a bad idea to look over all this stuff whenever your down there,
vibration or not. Just look over every thing in general with an emphasis
on delicate stuff, like brake hoses/lines, exposed wiring & connectors,
CV boots and on and on.
Good luck, let us know how it turns out.
Erik