Engine/Transmission (1994 - 1998) Driveline Vibration

[Got Smoke?]

Well about 3 or 4 weeks ago I started noticing a decent vibration at 45mph then at 60mph.



Kept getting underneath the truck looking from something like a weight on my driveshaft (people like to play to much in my town ) and giving up when I didn't see anything odvious. Well finally one of my classmates (GM ASEP) crawled underneath the truck one day trying to help me find this vibration because it was starting to shake the whole truck to death.



He noticed it right away... the straps to the rear U-joint were so loose you could wiggle them with your fingers. :--) Don't know how I ever missed that!



Well I tigthened them up and that helped some, but the vibration was still there. So last night I replaced my u-joint and on the initial test drive the vibration seemed to have left at 45mph and stayed at 60mph.



Well on my way to school this morning(50+ miles) it was rather odvious my vibration was still there.



What do I need to check? When I took the straps off last night I noticed they had a shiney place worn into them, not deep but just a shiney spot against the rest of the dull metal.



I did not replace the front u-joint in the rear driveshaft. Honestly being only 20 I didn't remember there was one there or I woud have.



But I really need some help on this cause this vibration can't be good and you can look in the rear view mirror (side) and tell that the truck is vibrating. :{

 

[bmoeller]

Have you checked for play in the slip yoke? Is the other u-joint that hasn't been replaced have rough spots in it? Is the driveshaft still balanced and true? Bad or out of balanced tire?

 

[Got Smoke?]

Tires were balanced about 1,500-2,000 miles ago thinking that was the prob. As far as the other u-joint having "rough spots"? Where exactly would I look for them? Both u-joints seem to move freely with no signs of destruction but I still replaced the rear one cause I alreayd had it. Is that what you meant by checking the slip yoke?

 

[drrhoades]

I would replace the front u-joint as well as all of the straps and bolts holding both u-joints on. If it is still a problem rotate the shaft 180 degrees and see what happens. If still a problem take it to a driveline shop and have the check the balance and straightness. Make sure to follow the instructions and grease them with the approved grease. Also grease the slip to if there is a zerk on that.

 

[Scot]

Check your pinion nut.

 

[Got Smoke?]

Originally posted by Scot

Check your pinion nut.

For what? Torque Spec? ???

 

[bmoeller]

Originally posted by Got Smoke?

... checking the slip yoke?

What I meant was where the two shafts slide in and out at, push it up and down to see if there is play in it.

"rough spots"?

Remove the straps on the u-joint that hasn't been replaced. Hold the shaft with one hand and the caps with the other. Rotate the u-joint back and forth to see if it feels rough. It should move smoothly.

Originally posted by Got Smoke?

For what? Torque Spec? ???

Yes, after that, see if the pinion bearing is going bad.

 

[bmoeller]

Get your vibration figured out?

 

[Glen Pratt]

How many miles on your truck? I had a similar problem. Turned out my motor mounts were toast. Looking at them you'll see right away if they need replacement. My engine was sliding back and forth about an 1/8". Something to look at. -Glen

 

[Loren]

Mark,



With any luck, your problem could have a very simple solution. Did you separate the driveshaft at the slip joint when you replaced the u-joint on one end?



If so, I suspect that the driveshaft is out of phase. The u-joints on a drive shaft must match each other in order to avoid vibration. That means that when the yoke on the shaft at the front end is vertical, the yoke on the shaft at the rear end must also be vertical. If the slip joint was put back together without regard for this, then your driveshaft is out of phase.



Correct this condition and see if that's the problem.



Good luck.



Loren

 

[Tim Galyean]

If you have read my post about my bucking truck, I found out that my problem was a broken motor mount. I have had my new tires balanced 4 times, and the vibration never went away. I was certian it was the tires until I realized my motor mount was broken.