Speed Specific Vibration

In all the years I've been herding worn out, POS cars, I have not had this problem before. At about 50 mph I notice a minor vibration. At 65 mph it's worst, mostly concentrated to the front, but resonates through the Jeep. At 75 mph it has diminished, but is still audible.

It's that diminished part that has me stumped. Every other worn out vehicle I have ever owned has just gotten worse as the speed increased. The steering is responsive, tracks well. The front cycles and jumps (?) when you run over an expansion joint or patch, yet you can let go of the wheel before hand and the Jeep tracks straight. The vibration is worse if the road surface is is not very consistent.

1990 Limited, 4.0 L engine, non-disco front, auto tranny, 242 TC.

Last spring I replaced the front axle assembly because the pinion bearing was shot, and the R&P with it. Since Feb. I have replaced: Ball joints, control arm bushings, EVERY steering linkage (one TRE twice), track bar (twice), sway bar end links, 3 U-Joints (1 rear shaft, 1 front shaft, 1 stub in new axle). I have greased everything at least twice.

I HAVE NOT REPLACED: One upper control arm bushing (yet), sway bar to body bushings, unit bearings, shocks, steering damper, steering gear with intermediate shaft, tires. I have not had an alignment yet either.

It's kind of pointless to replace tires without alignment, it's pointless to go for alignment with worn out parts. I really need new tires. Would worn out tires behave this way?:dunno:

Could try rotating the tires first. If you that doesn't help, and you need new tires anyway, try the new tires. Then the alignment. I didn't feel it in the steering wheel, but my TJ had a resonance at about 45+ and stopped at about 70. That turned out to be a bent output shaft. When I trouble shooted I rotated, balanced, then put on the OEM tires I had. If you want to know before getting new tires switch with a vehicle you know has balanced tires and wheels. Maybe on a weekend or something so you can switch them, then give them back after you test them. When you take them off check for obviously missing wheel weights and/or damaged/bent wheels.

It sounds like you have a case of "death wobble" and the most likely reason is a worn steering damper.

Sounds like the radial belts in one of your tires are separating.

i got my 01 back in september, and i get a shake when i hit 50 but goes away by the time i hit 55. the wheels were balanced, it reduced the shake a little, but it's still there.

does anyone know the typical life of the steering stabilizer (dampener) ?

:skull2:

Balance is the usual problem, but misalignment will also do it. Or both. A bad steering damper will let you feel it more, but it doesn't cause the problem.

If you've replaced steering parts without getting it realigned, that's a prime suspect even though the problem is more often balance. You should also have the wheel balance rechecked, though. A lot of places get it wrong, and sometimes, especially with alloy wheels, the weights will come off. I think that sometimes tire shops depend so on their computerized balancing machines that they don't double check their work. In addition, it's surprising how many places will do the job without cleaning the half pound of mud and crap off the rims first.

If you have tires that have worn unevenly from bad alignment, they will often track wrong and continue to wear funny even after the alignment is fixed. Try swapping front and rear and see if it makes a difference.

Thanks for the input! You have confirmned my suspicions, time to finish this up.

Every purchase has to count, guessing and throwing money at it won't get me out of the dog house. LOL

Dr. Dyno said:

It sounds like you have a case of "death wobble" and the most likely reason is a worn steering damper.

Click to expand...

:shocked: I hope you are just joking or being sarcastic.

No I'm not joking. I had exactly the same problem in my XJ 3 years ago. The whole Jeep would start shaking violently if I hit a tiny bump in the road at 65mph, and it would stop if I slowed down to 45. A new steering damper cured it. Worn control arm bushings can also cause this same phenomenon also known as "death wobble".
Wheels that are out of balance cause speed-related vehicle vibration that does NOT go away when you increase the speed further.