Driveline Vibrations

[TylerZ281500]

It's extremely misleading when the shaft is in the truck, especially if there's any tension at all on the driveline. I block the tires and kick the trans in neutral before checking; anything less is a waste of time.

Had kind of a surprise a few months back; wrecker got crashed and it split the driveshaft (dude that hit me bounced off the truck a few times while grinding down the side of it, ending in smacking the rear tires so hard it broke the U-bolts so the axle came right off the leaf springs, burying the tires in the bed corner) - driveshaft's rear yoke got all beat up on the pinion yoke dampner, crushing the ears around the joint's bearing caps. Had a driveshaft shop cut the yoke off and weld on a new one, install all 3 new joints, new carrier bearing, and balanced the assembly. Was fine for a little while then started vibrating again. New carrier bearing was toast (the rubber web had broken apart, not all of it, just most of it)...they replaced it and re-balanced for free, but couldn't offer any ideas on why it failed.

Richard

sometimes there is no reason carrier beaings can be finicky. weve had a couple striaght out of the box from american axle that the bearings are toast. since everythings mass produced sometimes bad products do occasionally slip by and all the producer can do is make the issue right in the end.

 

[Whipped96]

Moved the shim around this morning so the fat part is in the back. It rotated the pinion angle up and took out 95% of the vibration.

 

[someotherguy]

Kickass you had your suspicions they were installed incorrectly and some of us did, too. Glad you got that improvement. The other 5% might be "vibration memory"

Richard

 

[sewlow]

Memory could be fuzzy but most likely the shaft is keyed at the slip yoke, preventing misalignment of the two pieces. Generally though driveshaft shops will mark them anyway as it's kind of their business to know that things like that are important, and they balance the shaft as an assembly.

The pinion angle shim position may be the issue, and honestly I can't recall because I'm usually doing a 4/6 or more; I thought with a 3/4 you weren't really in the situation where you needed the spacer kit you installed?

Richard

4" rear drops need a pinion shim. Usually with the wide end of the wedge in the front. But each truck can react different to the shim. Best to measure. I've tried everything from a 1.5 degree wedge all the way to a 4 degree, installed in both directions to find out what worked best. For my truck, a 1.5 worked the best with the wide part at the front, which drops the nose of the pinion.
6" rear drops have the pinion angle built into the kit.

^^^^^ that's why I suggested to turn it 180 and see what happens... Had the same thought...


Sent from what use to be a great country.

Driveshafts should be installed with the grease zerk installed on the compression side of the rotation. Especially if there's any power in front of it. That zerk installed on the wrong side of the compression will be a weak spot that allows the power to stretch that zerk's opening, resulting in a pre-mature failure.

These truck also have a problem with 'beam-walk'. Vibration of the frame rails. GM's aware of this. Their solution? 500lbs. of 'ballast'! Boxing of the frame from the cab mounts to the rear just past the rear spring shackles works more better.

 

[someotherguy]

4" rear drops need a pinion shim. Usually with the wide end of the wedge in the front. But each truck can react different to the shim. Best to measure. I've tried everything from a 1.5 degree wedge all the way to a 4 degree, installed in both directions to find out what worked best. For my truck, a 1.5 worked the best with the wide part at the front, which drops the nose of the pinion.
6" rear drops have the pinion angle built into the kit.

I'm with you; what I meant was that accessory transmission mount & carrier bearing spacer kit. Haven't seen those needed unless doing a 6" rear or more. Could be wrong though...it happens every once in a while!

Richard

 

[Whipped96]

The kit that I installed had everything with it, coils, shackles, hangers, shocks, and alignment kit.

Everything seems to be good now with it.

 

[sewlow]

Yay! That driver side hanger was fun, wasn't it?

 

[Whipped96]

Yay! That driver side hanger was fun, wasn't it?

I have had this truck lifted, lowered, lifted, and now lowered again so I knew what to expect. My father-in-law has somehow figured out how to wedge his hand in between the frame and tank so it is not that bad.

 

[sewlow]

Lol! We had to get the skinny-minny 95lb office girl get her hand in there!