I have a 90 K5 blazer and I put 2 1/2 in springs in the front and 4in blocks in the back to level out the sagging old springs.

I have a vibration from about 10 mph to 25mph and then a vibe that gets progressively worse from 50 and above that turns to a growl when you let off the gas (when the driveline goes from drive to drag)

I've adjusted the pinion angle to approx 4 degrees on the rear shaft and had the front and rear drive shafts balanced and changed the universal joints on the front and rear drive shafts and still no change.

Any thoughts on how to fix the problem?

 

*Moving to Fullsize Tech* - Please be patient and abide by the rules of the forum. Thanks.

Now, about your problem, have you narrowed it down to which driveshaft is causing the issue (by removing the front driveshaft and running it like that)?

Does your transfer case have a slip yoke for a rear output? If so, have you looked at replacing the output shaft support bushing in the tail housing?

 

Throw the rear on stands and let the tires spin see if you can find it then. Possible axle baring?

 

Sorry about the double post. I wasn't aware of that rule.
I have thrown the rear on stands and it is on the rear, but the problem with it being a axle bearing is that the problem started as soon as I drove out of my drive way after putting the lift on.
Where exactly is this alleged output shaft support bushing? I've looked online and a few other places and cant seem to find it.

 

The output shaft bushing is in the tail housing on the back of the transfer case in behind the rear seal. It is a sleeve bushing. Whether you have it does depend on what transfer case you have.

For the NP241, here is the illustration:

Item #2 is the part I am talking about.

 

sounds to me likeyou have a pinion bearing going bad. the lift changed the driveline angle and now you are hearing it. or it could be your ring and pinion gear has a chipped tooth.just a thought as i have had both problems at one time or another and the symptoms are about the same as you described .

 

did you put tapered blacks in the truck to change the pinion angle if so theres your problem. the tcase output and the pinion angle are not equal, this prevent the natrual vibration of the drive shaft from being canceled out. my cusin had 4in tapered blocks in his K5 and did just as you described, minus the growling you mentioned

 

sorry to get here so late, but Jcourange, did you get the vibration figured out? I was amazed to see someone had not only the exact vehicle, but also the exact same modifiaction and result as myself. I put the lift on and.........vibrate and growl just like you said.

 

Actually I got it close but not perfect. I made some modifications that I didn't need to and that hopefully you haven't made. What you need to do is take your tapered blocks back and get straight or flat blocks and try that before you make any adjustments. That will keep the tcase angle and the pinnion angle the same. That came from the help of 515blazer. I went the round about way and if I had about three pages and 4 hours I'd try to explain everything that I did to get it driveable.