High speed vibration under load

[hdm48]

Ok, I'm humbled. Normaly I can diagnose anything, fix anything, build anything, modify anything. But I guess I need to be knocked off my high horse from time to time.

And here it is,



At 70mph, I get a vibration that seems to come from my drivetrain. But it is only under a load. If I coast, slow down, or just throttle back, it goes away. And the more throttle I give it, it gets worse.

I have rebuilt the drive line, tested it for out-of-ballance, checked the pinion angle, replaced all mounts.

This vibration seems too slow for a driveline, almost feels like it's a loose wheel, but it's not. And it's not an axel bearing either.

I almost wish I could crawl under it at speed to see if I can see what it is. But I think that would require a larger shoe size than what I've got to do. Maybe if I had one of those little high speed creepers like they had in the movie "speed" I could do it. But I don't, so I won't.

I'm stumped.

I guess what I'm trying to say is,, I need some help please



Thank you



Dave

 

[dan brooks]

Loose yoke on the transfer case output? I chased a similar vibe in my Jeep that we finally traced to the yoke.



The exhaust or something else contacting the frame when the engine torques over? Broken exhaust hanger or missing an insulator?

 

[CDegner]

Dave,

Had the EXACT same thing happen to mine. Vibration would come on at just under 70mph and got worse the faster I would go. Let off the throttle and it went away. I was convinced I had a wheel that was warped. I had checked everything else I could think of ... u-joints, bearings, entire front end, alignment and nothing helped. I was certain it was in the front wheels too as I could feel it through my steering wheel. If I was driving down a straight, flat stretch of road and let go of the steering wheel, the wheel would actually shimmy back and forth.



Granted, I drive a 2WD and yous is 4x4. It turned out that I had a u-joint that was bad. Could not tell just by reaching under and trying to move the drive shaft and it didn't make any noise when put in drive, reverse, or back and forth between R & D. If wasn't until I pulled the drive shaft and determined that the u-joint on the yoke was almost froze up. It was also stuck in the yoke so bad that trying to press it out ruined the yoke. That was a $280 ouch!



Hope this might help some ... I doubt it but maybe.



Carl

 

[JLEONARD]

Sounds like u joints to me too. You can't really check them with everything tight and bolted. If they've got some time on them then it's good PM anyway to replace them.

Good luck

Jay

 

[1stgen4evr]

vibration

I would think that you have a joint that is freezing up. If you have the situation as Carl mentioned, torch the cross out and warm the yoke ends and smack the caps to the inside. I have never lost a yoke this way.



James

 

[Grey Wolf]

Dave,



Not to insult your mechanical abilities, but is the driveshaft in phase? My son's truck had the same problem and he asked me what I thought, after one look below I told him it looked like the previous owner had changed U joint's and put the drive shaft back together out of phase. He put it back in phase and the vibration went away

 

[bgilbert]

I had the same vibe, felt like the rearend was about to come apart, before I replaced the elcheapo ujoints to spicer ujoints here recently. After removal I could see the rear joint was shot had a heck of a wear pattern, looked as though the shop lost or crushed a needle bearing on install. Now with new joints that are tight, the vibe is gone, feels like I'm getting that power to the ground now. BUT I don't think its gone completely. I havent really hammered on it from 65+ to see if the vibe is still present. Interested to see where this thread goes. Maybe loose yokes, they require big torque. Maybe time for ladder bars, all that torque you have, probly making the rearend rock and roll and bounce like crazy?? You could check to see if the suspension blocks have traveled any, same with your leaves in the pack see if there is any evidence of travel. Maybe loose ubolt?

Edit: vibration is gone after spicer ujoints installed. Did the hammering at 65mph to wide open and it just goes, no more vibe.