specific to throttle input. i think motor/transmission. does it instantly smooth out when you off-throttle?

being that it is vehicle speed specific is weird though, sounds like susp./wheels. in that aspect

or the driveshaft. dont wanna say rear-end. but vibration only during under-load circumstances still just sounds wierd to me.

hang on i just confused myself. nonetheless i dont think it's a front-end issue. nor tire balance

 

I would think if it were a broken motor mount you wouldn't just feel it at 60mph. Many suspension features are designed to reduce noise, vibration and harshness such as:
track bars and braces
proper vehicle ride height
hydraulic suspension system mounts
independent rear suspension systems
large insulating bushings
For vibration noises we have:
shake
roughness
buzz
tingling
boom
moan or drone
howl
whine

What kind of vibration do you hear?

 

X2
Sounds like U-joints. The wiggle test doesn't work. You have to remove the drivline and check the u-joints by hand. If one is bad you will feel rough spots as you move it back n forth. Its impossible to check for bad u-joints with the drivline still bolted up. U-joints can cause serious vibrations if there bad.

 

I've had the same problem in a geo prizm i used to own. at 62-64 bad vibrations on the highway. the drivers side wheel would wiggle when jacked up, and i ended up replacing the wheel bearing. problem solved

 

If we are in left field, you forgot that we are talking about a 2wd truck. show me where the front driveline goes, please?

 

sarcasm...

 

Something dawned on me. When you began your post, you said you couldn't feel anything through the steering wheel. After rotating your tires, you could feel the vibration through the steering wheel.

From that it sounded like the vibrating was coming from a rear wheel/tire out of balance. Then you moved it to the front and with the wheel/tire still out of balance and now being on the front you can feel it through the steering. U-joints aren't speed specific. You can feel them on acceleration (clunking noise) and the vibration increases with speed. A seized u-joint would cause binding. If something was out in the rear end you would hear a whining.

 

is the drivelive one piece or does it have the carrier bearing cv joint like most of the xtra cabs?

 

Sounds like a broken cord in the tire. My truck vibrated terribly with my old set of tires because three of them had broken cords until one of them shredded to pieces. Once I bought my new tires, the vibration went away.

 

A really deep resonating buzz I suppose? Similar to a pager vibrating against a desk but 10 times louder.

 

Driveline is one piece, no carrier bearing.

 

The vibration did not occur as a result of the tire rotation. I just paid more attention to things and added more info to the thread. That was my fault for not clarifying that in the first place.

I'm going to drop the driveshaft right now. Its about the only thing that hasn't been done yet. Brakes don't vibrate, idler arm replaced, ball joints checked out, tires and wheels check out fine, motor mounts look fine,rear diff fluid changed, and still the problem occurs.

So driveshaft and wheel bearing will be pulled and inspected right now. Thanks for the help so far, will chime in with my findings.

 

One more thing to check while you're under next time. Last year I had a similar issue in my 86 4wd. After 2 trips to the tire store, I started doing the same checks you are. What I ended up finding was a pinion bearing that was on its way out that would hum and vibrate between 55 and 65. It wasn't a bad fix, but I caught it while up on a lift with a mechanics stethoscope.

Good luck brother!

Bob

 

Buzz: A buzz sound like when holding a vibrator-type electric razor produces a feeling similar to a buzz vibration. This type of vibrations usually felt in the vehicle floor or the seat. A buzz-type vibration is usually caused by defects in the exhaust system hangars, A/C compressor, or the engine

Moan or drone: this tone produces a noise similar to a bumblebee in flight. Moan or drone may be caused by defects in the exhaust system or defective engine or tranny mounts.

Yes, I would love to hear the outcome. good luck

 

Well, turned out to be the U joint where the driveshaft connected @ the transmission. One of the legs broke off the spider and was jammed in place. I'll post pics soon.

 

hmmmmmmmm

 

This is the front u-joint where the driveshaft connects to the transmission. The cap from the U-joint cracked and made that section of the joint loose, hence why the vibration occurred at a certain point and tapered off as speed increased and disappeared when I let off the gas pedal. Could not tell by shaking the driveshaft, had to pull the whole thing off to see the issue. One could have lifted the rear wheels up and spun the driveshaft to the area where the joint failed, but ultimately you would have to pull down the shaft to repair it.

 

yep, that's what i thought.

 

computer running slow didn't see new post

 

I had the same issue with the front u-joint as well. It sucked to change it, but afterwards the truck worked great.