The Stovebolt Site Forums The Shop Area General Truck Talk Vibration

Hi Folks,
Been out of touch for a while. Just took my 55 3200 pickup out of the garage after an extended winter rest.
Changed oil etc and mounted four new wide whites. Balanced the wheel/tire assemblies and also put in a new rear main seal and complete clutch assembly.
Took the truck out for a test drive and above 40 mph noticed a vibration. First the external rear view mirror starts to vibrate and then the whole truck. It seems to be a relatively high frequency vibration. Doesn't seem to be RPM related. Always in the same speed range whether in 3rd or 4th gear. Steering wheel does not shake excessively. Nor is there a front end shimmy.
I am thinking the driveshaft could be out of phase (haven't checked it yet) or maybe the flywheel is loose. Had to use the old bolts as the new ones were defective according to a supplier e-mail. Don't know if a loose flywheel would vibrate only above 40mph??? New lug nuts are also correctly torqued. Vibration was not present before the above work was done. Anybody out there got a magic wand. I need help...
Many Thanks!

I'd be looking at a bad tire first ,if it was the flywheel it would be RPM related in any gear. Get the tires on a spin balancer and see if one of them has a bad cord.

Also check universal joints,and center bearing on drive shaft.

Pete

I would check those tires also - those "wide whites" are notorous for being out of round. That can be corrected by truing the problem tire.

It sounds like wheel /tire vibration to me too. You can check the flywheel/clutch by just raceing the engine in neutral. I had one like that once. The headlights behind you in the rear view mirror look like Cherrios.

Had a similar problem with my truck when I finally got it running. Thought I had a serious mechanical problem, but a friend said to re-balance those Universal WW tires. It worked, now I can go 50 mph with no problem.

You said you balanced the tires already? Check your front wheel bearings for play / wear....

Many thanks to all for all the VERY HELPFUL replies.
Checked the driveshaft phasing - everything is OK.
Revved the motor in neutral and didn't get any excessive vibes so I guess the flywheel bolts are OK.
A friend (he's the guys who spun balanced the new wide whites) suggested that the tires may be underinflated or have flat spots from sitting in the garage since last September. He suggested that if there are flat spots things may get better after a long drive. I upped the tire pressure from 20psi to just over 30 psi. As soon as the rain stops I'll go for a long ride and should know more...
The flat spots theory could be the answer. When I had to roll the truck forward to close the garage door, I noticed some resistance as if the tires were flat spotted. Once I overcame the resistance it rolled easily. The wheels didn't roll a full revolution so I can't confirm flat spots. As an afterthought It just felt like they were there.
Can anyone recommend a 6.70-15 tire pressure for freeway driving?
ThanKs Guys

I'd put about 35 psi in them. 20 is almost flat. Look on the sidewalls & see what kind of fabric is used in the cords. Nylon tires are very prone to flat-spotting.

sepp, 20 psi is almost flat, as noted above. Mine say 32 psi max, and that's what I put in. I've tried a little higher, and then they feel like solid rocks! Mine say "polyester" but they still have flat spots after sitting. After a few miles they are OK. Correct pressure will make the steering MUCH easier, too.