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01 w/ Procomp 3" lift = vibrations

viperbluelx

NAXJA Forum User
Location
Ringgold, GA
I just picked up an 01 XJ yesterday with a Procomp 3" lift and 31x10.5-15 BFG A/T's.

I noticed right away that there is a vibration that starts around 50 mph and gets worse the faster you get. If you set the cruise at say 70 mph it seems that you can hear the noise of the vibration come and go(you still feel it the whole time). But you can hear it for say 3-5 seconds then it gets quieter for a few seconds then comes back.

The lift consists of springs in the front, add-a-leafs in the rear, shocks, and a track bar drop down bracket according to the Pro-Comp website. I noticed today that it also has a transfer case drop kit, but I don't think those come with the Pro-Comp kits so somebody else added it.

This Jeep has been lifted with this kit since 2001, but I have no idea if it's always had the vibration or not.

Today I pulled all the tires/wheels and balanced them all and put the best too in the front and the shaking got better but the vibration is still there, any idea where I need to look first? Hope this isn't too much of a newbie question.

Mark
 
it could still be your tires. If re-balancing them already reduced your vibes I'd bet even more on the tires.

I've had the same experiences. You have used tires that end up wearing unevenly and there's a speed pocket (it was between 55-70 for me) where you get vibes. I ended up putting new tires on it, and voila, smooth as glass.

I have a Miata as a daily driver also, had the same issue, vibes above 65mph. I just put new tires on, again smooth as glass. You'd be surprised how much tires affect your ride quality.

Anyway, that would be my bet on the tires.

With that said, it is possible that it's driveline vibes. Where does it feel like it's vibrating? Does it do it under acceleration or just at those speeds?

If just at those speeds, I'd think tires. If during acceleration, I'd think driveline.
 
You can always crawl under and check some angles - if your differential yoke and transfer case output shaft are parallel, it shouldn't be driveshaft related. If not / if not damn close, could be that you need to drop your tcase or put in a slip yoke eliminator.
Check alignment.
Check tire inflation - I noticed a HUGE difference in ride quality by dropping my tires to the correct pressure.
 
Hey Mark. One thing you could also check are the ujoints in the driveshafts. Also, dont forget those wheels and tires sat on a TJ for about 6 months before they went on the Cherokee. Also, definitely use an angle finder to check DS angle versus pinion angle. ;)
 
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You can always crawl under and check some angles - if your differential yoke and transfer case output shaft are parallel, it shouldn't be driveshaft related. If not / if not damn close, could be that you need to drop your tcase or put in a slip yoke eliminator.
Check alignment.
Check tire inflation - I noticed a HUGE difference in ride quality by dropping my tires to the correct pressure.

I'll check the angles with my angle gauge Monday.

Already has the tcase dropped.

Tire pressure was at 20psi when I checked them and I put them at 35psi when I balanced them today.

Hey Mark. One thing you could also check are the ujoints in the driveshafts. Also, dont forget those wheels and tires sat on a TJ for about 6 months before they went on the Cherokee. Also, definitely use an angle finder to check DS angle versus pinion angle. ;)

I checked all the u-joints today and they are all great. I noticed that where the driveshaft yoke slides into the tailshaft of the tranny that there is some up and down freeplay there, almost as if the yoke isn't quite far enough up in the tailshaft, if that makes sense.
 
From what I've read it appears that the front driveshaft spins even in 2wd on the 01 models? Is this true and if so should I pull the front driveshaft just to eliminate the front as being part of my issues?

I've also noticed sometimes when I take off from a dead stop that something pops in the rear suspension/driveline almost like something slips or shifts, any ideas?
 
From what I've read it appears that the front driveshaft spins even in 2wd on the 01 models? Is this true and if so should I pull the front driveshaft just to eliminate the front as being part of my issues?

I've also noticed sometimes when I take off from a dead stop that something pops in the rear suspension/driveline almost like something slips or shifts, any ideas?
Yeah, unless you have hubs, the driveshaft will always spin in 2WD because the R&P is spinning. Warn hub kits are $1200. :gag: As far as the rear, check the u-bolt plates. I bet it is getting some excessive axle wrap. Mine used to do something similar and I tightened the Ubolt plates REAL GOOD (180lbft.) to solve the issue. There were quite a few bolts loose on the front suspension on that Cherokee that I tightened so you may want to go through the rear also. I didnt think about that. U bolt plates, spring mounts, shock bolts, driveshaft flange bolts at the Tcase and pinion ends, etc.
 
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I checked all the u-joints today and they are all great. I noticed that where the driveshaft yoke slides into the tailshaft of the tranny that there is some up and down freeplay there, almost as if the yoke isn't quite far enough up in the tailshaft, if that makes sense.

Pics of the rear ouput yoke?It sure sounds like you need a sye.
 
I'll snap some pics Monday and post them up.

Are the TC drop kits a bad idea? Should I put it back stock and use a wedge in the rear to correct pinion angle?
How much do you care about your rig?How much do you like being stranded on the trail?How much do you care about losing "critical" ground clearance after doing a lift to gain clearance?
 
How much do you care about your rig?How much do you like being stranded on the trail?How much do you care about losing "critical" ground clearance after doing a lift to gain clearance?

LOL! How is a TC drop gonna strand him on the trail and why would running a TC drop dictate that someone doesnt care about their rig? You always bring the oVeR-dRaMaZZ. :laugh2:

Mark, if you wanna ditch the TC drop, you are gonna need to switch it up a bit and do an SYE and CV driveshaft. The TC drop is an alternate way of reducing driveline vibes that come with lifting. That Cherokee has SOOOOOO minimal DL vibes, I would not mess with it unless you wanna drop $400 in an SYE and CVDS. Yes, the TC drop will cost a littel belly clearance, but its all up to you. FWIW, I run 7.5" of lift and NO SYE, but my driveshaft was taken toa driveline shop and had a CV installed at the TC side. Rolls like a dream.
 
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starts around 50 or so and increases with speed, pretty good roaring sound too. Can you ask the guy you got it from if he had any issues? If he didn't then it pretty much points to the tires. Did the TJ they came off of just sit for 6 months(enough time to get flat spots)?
 
Yes, like I said, the TJ the tires and wheels came from sat for atleast 6 months. You can PM "Kenny" from SEOR. He is the one I swapped wheels and tires with and he knows more about the TJ that had those on it.
 
XJ002.jpg


XJ003.jpg


XJ004.jpg


XJ005.jpg
 
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