Drive line vibration?

[walkingthecow]

First off, I've been a fan of the forum for awhile now, I've just never registered as a member... anyway, I'm glad to be here.

I have a '92 v6/auto/4wd pickup with 87,000. I noticed a slight vibration about a month ago and assumed it was a wheel balance issue so I had the tires rotated and balanced. After the rotation and balance the vibration got worse and seems isolated to the back of the truck. With that said I know the vibration isn't coming from the wheels.

I had the u-joints in the drive line replaced but the vibration is still rough esp between 45-55mph. The vibration is intermittent between 65-75pmh. My friend mentioned that the driveshaft might be bent, but I haven't done any off roading so that seems highly unlikely.

Any ideas or help would be appreciated.

 

[curlyeagle]

I learned the hard way, there are weights on the drive line to balance it out. If they are missing, it can cause vibration. Another is being that u pulled and replaced the u-joints, if u didn't square the front and back flanges, it will be out of square and that will cause vibration. Check it out.

 

[walkingthecow]

Thanks for the tip about the weights, I was unaware. I did make sure to get everything back in-line correctly so it wasn't out of phase... but I will double check that tomorrow however. It is probably out of balance, that could be why it has gotten progressively worse over the month. The trouble is I don't drive it at high speeds (45mph+) very often, so it has taken me awhile to diagnose. Thanks.

 

[Combat Chuck]

I agree with Curly, it could be an out-of-balance DS, or a dying u-joint.
Somewhere here, I have a shot of the cheap Spicer U that came in the rear of my truck. The bearings had toasted, and the u-joint ate through part of the yoke. It caused horrendous vibrations.

 

[curlyeagle]

Oh yeah, one other possibility. Make sure all the flange nuts and bolts are the same. They are like weights as well. I lost one and put another size in. Gave enough vibration to bug me till I got home.

 

[4rnr]

You rotated the tires and it got it worse? And that leads you to believe it is not the tires?



check if the DS bolts are loose, and the 30 mm stake nuts on both flanges can walk out.

 

[walkingthecow]

You rotated the tires and it got it worse? And that leads you to believe it is not the tires?

Yeah... I agree. I had the same thought this morning. So, after I re-checked the driveline, bolts, and made sure everything is a-ok and in phase I checked the tires for imperfections, bubbles, etc. Lo-and-behold I found a bubble on the right front tire. This is what I get for taking the mechanics word that the tires are balanced and in good condition... I should have checked this first.

Call me a noob I guess... at least I know I have new u-joints.