vibration after lift install

[cochino12]

I installed a 4" spring 4" rear block lift and now I have a viibration problem. I cant tell if its from the front or rear, any ideas of what it could be? I can start to feel it at about 15 mph so I dont think it is the new tires/wheels being balanced wrong. I did adjust the thing (forget what its called) that connects to the steering arm so I could get it to turn right again though. The steering arm will be replaced with a drop arm this weekend.

 

[jjlaughner]

might try lowering the transfercase crossmember an inch or so, it took some of my vibes away.

 

[imaginepro]

Ya that works good lower your t-case /forums/images/graemlins/peace.gif

 

[cochino12]

So it wont hurt anything to drive it the way it is?

 

[angrysnowplow]

It's not exactly good for the truck, but some vibes won't destroy the rig. Lowering the transfer case is a real quick easy job, give it a shot, it may be just what you need.
Another culprit may be the u joints in the driveshaft. They develop a wear pattern, and installing a lift changes this. That may lead to vibes.
Good luck /forums/images/graemlins/thumb.gif

 

[K5 NUTT]

My friend of the other board....(2wd trucks)....lol.
Dropping the t case is the simplest way to combat the problem...however...it does not allways cure it. Measureing your driveline angles is the best way to see what is truely going on.

For example...my chalet...fresh motor...fresh tbi swap...vibrates like an earthquake at speeds approaching 70mph...I measured the angles and found them to be way out...basically you want to measure the angle of the tcase vs. the angle of the driveline....divide the two and see if you are in the 1 to 3 degree range...where a u-joint is happy...then do the same for the rear axle vs. the driveline...sometimes lift springs do not come with shims installed with the leaf pack and cause this problem...back to the chalet...my angles were in the neighbor hood of 10ish....embarissing yes....but the chalet never saw road speeds much over 60 mph....due to ah...handling issues...then the rear air bags went in and it was safe to drive faster than 65...then we discovered the problem...then the motor blew up...and she sat for a year...so i installed 4 degree shims in the rear leaf pack...and when you do this your center pin will not be long enough to get thru the shim and back into the spring perch...so i hit up Alcan spring on the way into work for some new center pins with spacers...and longer u-bolts....put her together and remeasured...within spec...failed road test...grrr. So i tore the 12 bolt down all the way to inspect bearings and such...all ok except the spider gear cross pin will wallow out the case in time...mine was 30 years old so i replaced the carrier with a new spare i had from a failed lock right experiment...hardened crosspin from same said event...new carier bearings and we did the road test thing again...again i failed...grrrr. So you probably want to know why i never considered the driveshaft and u joints...before we left phx and moved to co. i swapped in a rebuilt trans and a NP205...so the driveshafts were brandy new with low miles....however the prolonged driving had indeed severly brinnled the u joint trunnions...so i installed a set of the japanese ones you get from napa from my trail box for the 79...road test...once again i failed...so i took the rear shaft in and had them check the balance...sure as [darn]...a mere 20K out of round....plus we cut a half inch out of the shaft since i measured yoke to yoke to make sure we were right on target...put her back in and i'm now vibration free....

Kinda of a long post but since it the actual event occured a month ago i thought it would be educational if you will to run you thru the entire spectrum of what can and will go wrong ...

DW GJ CO