Vibration Woes, need help!

[Wingnutt]

Vibration Woes, need help!.....Update

As some of you know I’ve been fighting a drive line vibration problem for quite a time now with no success. I just got my Blazer back today from getting the 4:10s installed and I guess because the drive shaft is spinning faster, the vibration is worse. It’s almost non-existent below about 60mph but gets to the point where it will blur the mirrors by 70. Above that it really doesn’t get worse. At 63-65mph it’s enough to be really annoying. It doesn't go away when I put the truck in nuteral and coast either. I called the shop back and the guy who installed the gears (he has a GREAT reputation btw) said that it was an easy setup and he had a real good pattern the first time.

Now that I’ve got all that out of the way, I need a plan of attack. Of course I’m planning on changing the U-joints out this weekend. When I crawled under the truck the driveshaft felt nice and tight. However, I did notice that the drive shaft angles weren’t the same. I have some 5-degree shims that I plan on installing, but I’ve forgotten which way to rotate the axle. Do I need to rotate the axle up or down? In other words, which way should the thick end of the shims go, front or rear?

I’ve got to take a 400-mile trip the 23rd and I really don’t want to put up with a vibration for 5 hours each way.

Of course any other ideas would be greatly appreciated!




Lowered the transfer case tonight by moving the factory spacers from below the skid plate to between the plate and the frame.......MUCH better! I'll be putting 5 degree shims in Friday evening, will keep y'all posted.

 

[dontoe]

Have ya tried?

You may have already done this but............. Can ya temporarily swap tire and wheels with another vehicle, yours or a friends? May not be it at all but a relatively easy, quick shot.

 

[sublmnl1990]

I have some 5-degree shims that I plan on installing, but I’ve forgotten which way to rotate the axle. Do I need to rotate the axle up or down? In other words, which way should the thick end of the shims go, front or rear?/QUOTE]

Thick goes forward to make yoke go down Thick goes back to make yoke go up what tires and tire pressure are you running now?

 

[elacruze]

Did anyone check to see that the pinion shaft isn't bent in front of the bearing?

 

[Wingnutt]

sublmnl1990,

Got the shim thing, but do I need to rotate up or down?

I've running 33x10.50 BFG AT KO's at 35psi in fron and 29psi in the rear. I arrived at these pressures by the 'ol chalk and wear method.

The vibration is definatly something in the drive train because as I increase speed the frequency of the vibration increases, also the vibration is there durring both accleration and deceleration. If I carefully work the throttle to where I'm neither acclerating and decelerating it's not quite as bad.

The vibration has always been there since I purchesed the Blazer but it is much worse since the 4:10's went in. That's why I've got a sneaking suspision that it's somewhere in the driveshaft.

And I DID tell the guy at the shop about the vibration and to check out everything in the axles very carefully. He did and said that everything was good to go.

Edited to add: The vibration has been there through three sets of tires, and although I've got the same set of wheels, it doesn't feel like it's from them.

 

[diesel4me]

Bad vibes??

Did you check the splined yoke for "slop"??..Ever had the driveshaft balanced or checked for straightness??--you may have an out of balance driveshaft,(or worse ,a bent shaft from high centering on a log or something--even a small dent can be a big problem causer)and as you suspected spinning it faster with lower ratio gears will aggravate the problem...angles are important too,but many times I see shafts that are pretty sloppy in the sliding yoke splines,but they get overlooked as the cause of vibration--if the angles are close to correct its wise to check the shaft very carefully(abd the u-joints too--make sure they are tight,no rusted caps or needle bearings,and swivel freely in the yokes--if they bind they will set up a rumble..If your truck has a "tail" on the transfer case with a splined yoke (like a car tranny or a 2wd)the bushing could be worn and allow the splined yoke to vibrate also(usually leaks there too if this is the case)..good luck,,,hope its nothing expensive!..

 

[MTBLAZER89]

Well here is my .02 on this. I have been battling this for awhile now too, and finnaly got it under control. Your problem sounds more like a balance issue than angles because it is nonexistent below 60 MPH and continues with no power applied. Mine was around 25-40 MPH then it's ok or no vibes under acceleration because the axle wrapping up a bit fixes it. Mine also completely goes away in Neutral or when I let off the gas. I would swap tires around first cause it's the easiest then get you driveshaft checked

 

[3 on the tree]

Check your driveshaft to see if one of the factory balance weights has come off. Its a long shot, but easy enough to check.

 

[elacruze]

Let's take the scientific method. Have you measured the actual difference between the F+R joint angles? Have you had the driveshaft balanced? Are you full-time 4x4?, so the front could be the problem? Occam's Razor will eliminate the most likely suspects-it's a matter of measurement.

 

[1-ton]

"Well here is my .02 on this. I have been battling this for awhile now too, and finnaly got it under control. Your problem sounds more like a balance issue than angles because it is nonexistent below 60 MPH and continues with no power applied. Mine was around 25-40 MPH then it's ok or no vibes under acceleration because the axle wrapping up a bit fixes it. Mine also completely goes away in Neutral or when I let off the gas. I would swap tires around first cause it's the easiest then get you driveshaft checked"

I agree with this. If it where angles, the drive shaft would vibrate at speeds lower than 60 MPH. You should take it to a drive shaft shop that can check it for straightness, and balance. Also make sure the transmission mount is tight, and in good shape.