1999 vibrations above 50 mph
 

I've got an XJ with a 4.5" lift on 33s. I'm trying to find this nasty vibration that happens above 50mph. It gets very bad by 70, to the point you can't hear the radio and your arms start to hurt. I've been rebuilding it for DD purposes so it has everything new in the front end: ball joints, tie rod ends, drag link ends, etc. The vibrations started about a month after I put in the slip yoke eliminator. That install went smooth with no issues. 4x4 works fine. I also have brand new, balanced front and rear drive shafts. I've tried my old driveshaft and it doesn't change the vibration.

The vibration is speed based, not RPM. It is substantially worse with the front driveshaft installed. Without the front driveshaft its still very noticeable but drive-able. Wheels are balanced and tires are new. I've triple checked all bolts and everything is tight. I've opened the diffs to see if anything looks damaged an all is well. I'm out of ideas of what to check. Any more ideas?

This happened to me when my shocks wore out. I replaced them and it stopped. But there are other reasons why this can happen.

Shocks in the front are fairly new bilstiens. The rear i only have 1 shock as the mount broke for the other one and i haven't fixed it yet. I hope its not the bilstiens.

Another note is I replaced the engine/trans mounts. The only part on the front I haven't replaced is the upper control arm bushings, but they still seem to be good. Little cracking on the edge but nothing all the way through. I'm currently in the process of installing my long arm, so maybe that will help (doubt it).

Was hoping that someone else with much more experience would chime in as I haven't worked with lifted Jeeps for over a decade, but here is a good video which illustrates what may be happening.



Have you rotated your differentials to accommodate the new angles?
Have you eliminated the slip yoke for a double cardan?

Hope this is of some help.
-Rob

After chasing driveline vibrations in my 99 for over a year it's finally solved. The problem? Me. When I installed my new Tom Woods rear driveshaft I didn't ensure the u-joints and centering ball were adequately greased. Not enough grease meant water got in and accelerated the wear. Anyway, after rebuilding the driveshaft and greasing the snot out it, Ive been vibration free for over 3000 miles.

I offer my mistakes in the hope it helps someone else that's challenged by needle zerks. The only way to check the cordan-joint, as well as lubricate it properly, is to remove it. At least in my experience.

The jeep has been lifted on 33s for years with no vibration, except the bit of grinding and ujoint destruction caused by having the slip yoke. I have the slip yoke eliminator from rough country installed. This vibration didn't occur till around a month after installation. It was smooth as butter when first installed. I would think if something was wrong in there my 4x4 wouldn't work properly.

Hmmmm.... This is interesting. Both my driveshafts were new. I greased them pretty good before installation. Although my vibration was there with the old driveshaft (hence why i got these).

I ran into this today while doing some general reading about specs. At the bottom of this sticky thread there's some talk about shimmy (death wobble). https://www.cherokeeforum.com/f2/all...please-159091/

I had a 66 Rambler Classic with a terrible vibration issue at around 60mph. It was a combination of badly worn ring and pinion gears and worn universal joint (It only had one universal joint and it was such a PITA to change with that silly torque-tube set up:wallbash: . I have some additional thoughts regarding resonant frequencies and as to why these problems always turn up around 60mph (60 Hertz), but I'll save that for another day.

Reading about death wobble I do see my caster angle is messed up since I had the stock UCAs on after my 4.5" lift. The long arm I'm installing now will fix that, but I don't know why that would have started all of a sudden, since all my front end parts are new.

I believe I have found the source of my vibration... :laughing:

https://cimg7.ibsrv.net/gimg/www.che...35d031d21b.jpg

Well that was the source of my suspension vibrations, but not the main vibration. Now that the long arm is installed, It drives smoooooooooth and straight. I've determined it has to be in the transfer case. It's the only piece i replaced about a month before the vibration started. It only occurs when you accelerate/decelerate but it doesn't match engine RPM. it gets worse the faster you go. I'm going to pull that and check everything to make sure I didn't put something in wrong.

Keeping this updated in case someone has similar issues.

I went to pull the transfer case out and realized the yoke was just loose. I tightened it back down and a lot of the vibration is now gone! Dummy me didn't torque it down enough. There is still a vibration coming from the front. This is why its been so hard to diagnose. I believe the engine/trans may be hitting the body somewhere is the only thing I can figure. I have brand new engine/trans mounts. It only vibrates under engine load but it doesn't match RPM.

With the front driveshaft in, i can feel the vibration. With the front driveshaft out, i can only hear it. I already checked the dif/axles/etc and they are all tight and good. I even pulled the axles and drove it a bit so the front dif wouldn't spin. It still did it. I'm going to start hunting around the engine now.

You seem to be doing well in the hunt. Not to state the obvious, but, assume your tire pressures are correct and not leaking. Other thing I noticed with my xj is the front sway bar bushings made a heckuva difference. This after all the bj's etc etc were done.

what transfer case do you have? 45-50mph is a common speed to get vibes from a lifted jeep on 33s.

Hey if you're resonating @60Hz, you can use a capacitor from any line voltage motor to shunt the vibrations to ground.