Btommy

Hi all
could someone please help me out with a list of causes for my drive line vibes.They happened after I put my 2" lift in.(did not have them before)
in trying to chase them down I have replaced the rear u-joints on the drive shaft. And did a 1" t-case drop. I would like to remove the t-case drop and get rid of it but it seamed to help some when i put it in.
the vibes occur between 30-40 and 50-60 MPH. I also had my tires balanced.
So I am just looking for a laundry list of things to start looking into in an effort to eliminate them.
thanks for any advice /help

8sec-z

When u lift a late model xj, you need a sye kit. Get a hack n tap or full sye and ur problems will be solved. I tried the hnt, but I must have drilled it off center. At 70mph I had vibes. I bought a rugged ridge sye and adams driveshaft, put them in last week and I have zero vibes.
The late model xj's are super touchy to lifts as far as vibes go. G/L

Slick761

Ya why is that? My 90 was at 7.5 inches. I put a longer d.s in with no sye and had very little vibration. I lowered it to 5.5 and set the pinion angle and it should be even better. What difference causes later xjs to vibrate where earlier ones don't? Anyone know?

Xjtim

I've got an 01 with 5.5" of lift, no sye, just a drop kit, with no vibes...I dont consider them touchy...anyhow... Are you getting death wobble or driveshaft vibes? I haven't seen too many jeeps with a 2" lift that have driveshaft vibes...

jmm0122

Sounds like you got one of the unlucky xj's that need a sye at 2" of lift. You can try to put a larger t-case drop on it or shims but the best bet is a sye, if it is indeed drive line vibes.

Something about the output shaft on the transfer case is internal in pre 97 and external on 97 and newer xj's. Someone will correct me I'm sure, because my terminology is wrong. Haha.

It doesn't happen often but there have been 2 or 3 members on this site that have experienced this with bb's.

Xjtim

Huh...weird...that effen sucks...

Converted96

As far as why earlier xjs are less prone... I think its because the older is high pinion and newer is low pinion. I have read that some 96's have the LP while some 97+ have HP. Really drivline issue is luck of the draw. I have a 96 with about a 4.5 lift, 1" tc drop, no vibes. I consider myself lucky.

By pinion I mean on the axles where the shaft goes.

Slick761

Rear is all low pinion. That's where the vibes come from.....

hardstatic

Thought it had to do with the post June 1996 XJ's having a longer rear output shaft.



Anywho, vibes are all about the pinion angle in relation to the output shaft angle, constant velocity on the driveshaft, the ends slow down and speed up at a different frequency, BORING. Just get a slip yoke eliminator kit, shim your rear axle, and be done with it. One of the best $200 you can spend on your rig.

Just remember, every single truck responds differently when lifted. I could take two identical XJ's, put a 4.5" kit in one and have it be purrfect. Take that exact same kit out, put it in the other one and it's all F'd up.

Slick761

Best 20$ I ever spent... liftgate supports. Anyhow my pinion angle is within about 3* (no sye, both at same angle) and its great. Wouldn't think a little longer output shaft would make that much difference.

jowint

I literally got done reading some install notes on driveline vibrations while doing my research on lift kits.

NOTES:

LIFT KIT TROUBLESHOOTING
RE6025B Page 2 of 2
Rear driveline:
Acceleration vibration: Caused by the pinion being too high in relation to the transfer case output shaft. On leaf sprung vehicles, install axle shims to lower pinion accordingly.
Deceleration vibration: Caused by the pinion being too low in relation to the transfer case output shaft. On leaf sprung vehicles, install axle shims to raise pinion accordingly.
Slip yoke vibration: Caused by excessive angle on the transfer case slip yoke. Very common on vehicles with 2” or more of lift. Lifts of 2”-3.5” can sometimes be cured with a transfer case drop kit (pinion adjustment may also be required- see acceleration and deceleration vibration troubleshooting above). If this does not cure it, it will likely require installing a slip yoke eliminator (SYE) kit and CV drive shaft. Adjust pinion so it is 2 degrees below parallel with CV drive shaft (see acceleration and deceleration vibration troubleshooting above). A transfer case drop kit can usually be omitted with a CV drive shaft.

Slick761

So basically I got a good yoke, he got a bad one?

Btommy

Sorry for not responding sooner,For the time being I have to use my computer at work.
Any who. I also noticed that when I have weight in my jeep (like 2 guys in the back seat and bikes on the back) it gets alot worse, it is also worse going up a hill when I really have to get one it to get up the hill.that part I do not understand is I put a 2" lift in, my leaf springs sag 2" so my rear is actually were it should be, so I should not get them right?
yes I do get the death wobble now when I go over bigger bumps at speed.
My rear drive shaft does not have CV joint it is just normal (no goofy knuckle back there) it is only in the front and I have not changed out those u-joints (on my front shaft)that will be as soon as I can afford it.
SO from what I am understanding I am screwed and need to spend another 200 bucks for a SYE? plus install. right?
what are people referring to when they say "angle the pinion"or shim the pinion angle ?
please forgive my ignorance I am very mechanically inclined but have not worked on a whole lot of cars so I am learning as I go here. thanks for all of the input.

jowint

They are wedge type shims that when installed simply ride on the spring perch to create a pitched angle of your entire axle tubes.
They have a hole in the center of the wedge to align itself just as the springs do, and when installed they can pitch the angle of your differential up or down depending on which way you have them installed.
They will tilt your entire axle assembly up or down and is a extremely simple install given your bolts are not all rusted and corroded but since you just did a lift kit it should be a very easy install and a cheap attempt at correcting your problem.

Read my above post notes that I copied from a RE (Rubicon Express) install guide about (vibration upon accelerating.) -I hate acronyms.

Here is a link to see what the shims look like with a description.
http://www.quadratec.com/products/16121_090X_PG.htm

Slick761

And the pinion angle is measured easiest by taking out the d.s. and throwing an angle finder on the flat mounting surfAce of the yoke and take a reading. Next turn around and stick your angle finder on the drain plug on the transfer case and take a reading. The reason it gets worse when loaded is the weight is changing the d.s. angle