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i recently purchased a desert tan 99 Xj. I had a tj about a year ago and enjoyed it but always felt the want for more space. I found this xj as a second owner with 150k and got a fair price I believe. Anyway...
1.) I noticed at higher speeds sometimes as low as 35 it has a weird vibration. Not like an improperly balanced tire vibration/shake but a real vibration. I’m guessing it’s either the u joints or it’s in need of a SYE kit. It has a small lift, unsure how high or make of lift. But it has 31’s on it now so I’m guessing a 3” or so. The vibration is only when the throttle is applied. It’s worst is on the highway but as soon as you let off the throttle it goes away, reapply the throttle and it’s back again. Would a small lift really need a sye? Or are my u joints just causing it? I had a shop check the Jeep over yesterday while it was in for an oil change and the u joints all felt good with no looseness as well as all suspension components.
2.) I’m wondering what the stock height in inches is between the center hub and the fender front and back? So I can identify what size lift I have to order replacement parts should I ever have to.
I googled “cherokeeforum measure lift” and found the info.
Measuring from center of wheel to the bottom of stock fender flares:
17.5” front
17” rear
Bad ujoints won’t necessarily feel loose. Often, if anything they tend to bind up from lack of lubrication.
Vibes present only under acceleration makes me think motor mounts. I admit I have no experience with vibes caused by driveline angle though.
That being said, I believe a SYE is a good upgrade for any height suspension.
Another google search yielded the following info:
Originally Posted by dukie564
With a single U-joint at each end of the driveshaft, the pinion angle MUST be parallel with the transfer case output, so each u-joint cancels the vibes from the other.
If you have a sye and a double cardan at the transfer case, you point the pinion directly at the transfer case so you have 0* difference between the pinion angle and driveshaft angle, meaning your pinion is pointed higher
The front axle pinion angle needs to be balanced with castor, with pinion taking priority. The front axle pinion should be adjusted parallel with the driveshaft, and steering checked. If the steering took a big hit, back off the pinion little by little till you reach an angle that works for both steering and vibration
I have installed both a 3.5” lift in my ‘89 and a 2” lift in my ‘96. I also installed SYEs in both. I admit I have paid zero attention to pinion angle, as I experience no vibes I can relate to it. It is said, though, that even without vibes ujoints can wear out quicker with an improper pinion angle.
Last edited by ElMartillo; 02-17-2018 at 10:03 AM.
Found this awhile back. Seems it would be good if the flares on the vehicle being measured couldn't be used. Of course
we'd have to know the measurements of a stock vehicle to that point.
Found this awhile back. Seems it would be good if the flares on the vehicle being measured couldn't be used. Of course
we'd have to know the measurements of a stock vehicle to that point.
...or just the measurement from the bottom of the flare to that line on the fender/quarter panel. Add it to the dimensions I posted above. I’d measure mine but I’m nowhere near my XJs
That would do it wouldn't it. Actually I had forgotten about that pic and came across it while deleting old ones. The OEM flares on mine are in good shape so I'll get the measurements as soon as I can. Kind of stuck inside for while.
If it is motor mounts, you should be able to rev it in gear with the hood up and see the engine move.
If it is pinon angle, it will usually only do it moving forward, but always under load.
Under load, the pinion will rotate up 1-2 deg going forward, and if this is enough to throw the driveline angles out, you will get vibes...once you let off the gas, the pinion will drop back down, and the driveline angles will be better again. Same for reverse, but the pinion will drop down instead of rising up, with the same potential results.
Usually, a u-joint vibe is cyclic, not constant or steady
top of axle tub to bottom of frame gives best idea for lifts
hub to fender flare has always given me accurate measurements even when compared to the axle tube measurements. To me, hub to fender flare is easier as well.
02-17-2018, 07:13 AM
2 questions regarding a newly purchased xj
