driveline vibration

[Cornfed-90K5]

I am getting a harmonic vibration in my driveline. I have a six inch lift and have recently had my drivelines lengthened and balanced with new u-joints in an attempt to solve my problem.

I have been told that I either need to change the front u-joint on my rear shaft to a cv-joint or drop my t-case some more. Please let me know if you have had the same problem and how you corrected it.

Cornfed-90K5
1990 K5 Blazer
1977 Jeep CJ5

 

[Butch]

before you do that, use some degree shims on your rear axle and point your pinion towards the transfer case. It needs to be about 1.5 degrees below in line so that when you accelerate and the axle wraps it will be in alignment. Mine is this way and I can drive 90 if I want.

 

[Cornfed-90K5]

I already shimmed the rear axle. There is very little angle on the rear joint, actually less than the stock blazers that I have seen.

Cornfed-90K5
1990 K5 Blazer
1977 Jeep CJ5

 

[Brian 89KBlazer]

Cornfed

If I'm reading right, you DON'T have the rear CV shaft yet? If that's the case and your shaft is only 1.5 degrees above the rear pinion, then that's your problem. The shaft is only supposed to be in line with the rear pinion if you have a CV style rear shaft. If not, then the angle from the t-case to the shaft is supposed to be equal to (or very near the same angle) as the angle from the shaft to the rear pinion. Make sense?

See http://www.4xshaft.com for further details.

Good Luck
Brian
89KBlazer

 

[Blue85]

Yeah, with the lift and almost no angle on your rear U-joint, the forces from the upper and lower U-joints are going to be way out of balance. You'll probably eat the joints in 1-2k miles and shake no matter what speed you go.

'85 JIMMY
'90 paint/grill/trim 5"susp 33/12.5/16.5
Fresh 350 B&M '87 TH700