Vibes - Please help! Any ideas welcome!

[MoonShadow127]

I'm in need of some serious help! A bit of background to the problem though:

A couple weeks ago, I went out on a very light trail ride to Kephardt Run. The trail had been freshly bulldozed and provided absolutely no challenge whatsoever. I never even put the Jeep in 4WD. My girlfriend and I just wanted a nice ride in the forest, and we were close by, so that's what we did. On the way home however, the Jeep started making a "ratcheting" sound. Neither of us could figure out where it was coming from, but it was quite loud and got faster as the Jeep went faster. It did this for maybe 3-4 minutes and vanished. I haven't heard it since.

Fast forward to now. The Jeep has developed a wicked vibration and a low humming sound. It happens at any speed over 20mph, only under acceleration, and I feel it more through the steering wheel than anywhere else. If at any time I take my foot off the gas pedal, the vibration and the noise completely go away. I thought it must be a U-Joint going out, but since its 20* and snowy outside and my new house doesn't have a garage, I opted to just have it fixed. After two mechanics looked it over for an hour, they told me that nothing was wrong with the U-Joints, and that they had no idea what was wrong. I was so sure that it was a U-Joint that I hadn't really considered anything else. They told me they even swapped out shims for the rear axle, but it didn't solve the vibes. I asked if they checked the U-Joints in the front driveshaft, but they didn't give me very reassuring answers.

So I'm at a bit of a loss as to the possible culprit. If it isn't a U-Joint, what could it be? Pinion bearings? Transfer case bearings? I'm totally lost.

Here are the Jeep's vital specs, just so you all know: 98 XJ, AW4, NP242, RE3.5" Super-flex lift with full replacement packs, Tom Woods SYE, OME shocks, RE1600 trackbar, RE tie rod. 8.25 rear, D30 front. This setup hasn't been altered in the last three years. I replaced the shocks once, that's all.

Any thoughts or ideas would be GREATLY appreciated!!

 

[Starboard M]

Just throwing out ideas:
Dented driveshaft
Tierod ends
Axle bearings
Unbalanced tires

 

[MaXJohnson]

Sounds like Death Vibration or Death Hum. What were you and the girl friend doing?

Did you check to make sure you didn't loose a leaf spring shim?

 

[98XJ]

You have 242 TC right?
I would look into front driveshaft CV part. I had sound similar to what you described, only I had no vibes. In my case it was frnt shaft CV part (center support ball was grinding metal) Did you install CV shaft along with SYE?
Are the vibes oscillating, constant?
Can you feel the vibes on the dash?

 

[JLane99XJ]

check the u-joints?

if not do that 1st
chock the wheels remove the tension on the drivelines(ie place the trans & t-case in Nuetral) then wiggle the joints & check for slop.

 

[Harvo]

You said you were 2 wheeling right? Do you do that very often in the Jeep offroad? Did you climb any steep hills or spin the tires much on that trip? If you have had the same setup for 3 years this is unlikely... but you may have bent your rear springs a little. That happened on my last Jeep. I was 2 wheeling on a trail just messing around and the springs wrapped enough that they bent enough to change the pinion angle and make a vibe. Like I said... unlikely but worth looking at.

Otherwise, I would look into the CV like 98 XJ said. I can hear mine rotating (new noise) with my new lift, but it doesn't vibrate.

 

[MoonShadow127]

Thanks for the reply guys... I'll try and answer your questions:

I didn't loose a leaf spring shim, the leaf springs aren't broken, and don't appear to be bent.

Yeah, I replaced the rear driveshaft with a Tom Woods CV style one. And the vibration is constant as long as I'm on the gas. It goes completely away when I let off the gas. I can feel the vibes pretty much everywhere, but I can SEE the steering wheel shake... that should tell you how bad it is. The dash, the seat, the center console, it all vibrates.

No, I don't 2-wheel very often, but this trails was seriously just a gravel road. I've seen driveways that are more challenging. The hurricanes this summer destroyed the trail, so they recently bulldozed it... pretty much making it accessible to anyone and their Kia Sephia. We didn't climb a single rock or touch a single mud puddle. If I did, I would atleast understand this better.

Oh yeah, and all the TRE's, steering stabalizer, shocks, and the ball joints and hub on the driver's side is new. Because I just got over a battle with death wobble a couple months ago... now I have a vibration.

 

[MaXJohnson]

still, it wouldn't hurt to check the girlfriend for ticks...

 

[MoonShadow127]

So... check my girlfriend for ticks? That's it?

 

[XJ_ranger]

You have 242 TC right?
I would look into front driveshaft CV part. I had sound similar to what you described, only I had no vibes. In my case it was frnt shaft CV part (center support ball was grinding metal) Did you install CV shaft along with SYE?
Are the vibes oscillating, constant?
Can you feel the vibes on the dash?

had the same thing going on - pulled the front shaft and no vibes

correct pinion angle via adjustable arms and reinstalled a NEW shaft - no problems
write up here:
http://www.opiebennett.com/upperdrrveshaft.htm

 

[madcrazy_lp]

check the u-joints?

if not do that 1st
chock the wheels remove the tension on the drivelines(ie place the trans & t-case in Nuetral) then wiggle the joints & check for slop.

I agree. sounds an awefull lot like U-joints. i know you said you had it checked out but dont trust anyone but yourself. chock the wheels and put everything in nuetral and check all U-joints. yes all. I had my u-joints "looked" at, and the idiot didnt catch the bad u-joint

 

[XJ_ranger]

might try pulling the front shaft and driving - then you know if the prob is front or back...

 

[ChuckstrPT]

That sounds very much like the front end. I also have the 242, and am planning a lift soon, and would like an update when you figure this one out. I've got my concerns about that 242, and being able to use Full Time after the lift, in particular with my LP D30......I'd go after that front driveshaft to narrow it down. I'll give you that is doesn't make sense with you on the gas. That "shouldn't" effect the front driveshaft, unless you ARE IN Full Time?

 

[mrfreakinwhite]

No one suggested motor mounts or trans mounts?
My ol' 88 (stocker on 30's) first needed a trans mount, vibe fixed.
Vibe came again, worse. Shook the dash, mirrors and steering wheel. Replaced the motor mounts after having it looked at, vibe fixed.
Worth checking...

 

[MaXJohnson]

No one suggested motor mounts or trans mounts?
My ol' 88 (stocker on 30's) first needed a trans mount, vibe fixed.
Vibe came again, worse. Shook the dash, mirrors and steering wheel. Replaced the motor mounts after having it looked at, vibe fixed.
Worth checking...

good call

this makes more sense than anything :kissyou:

 

[mrfreakinwhite]

...And yes. Always check your girlfriend for ticks after experiencing Death Hum in the woods.

 

[Flyfisher]

It's been suggested...but I'll 2nd (3rd, or 4th??) the front driveshaft u-joints as the culprit. I had the same symptoms...and they kept getting worse. I narrowed it to the front end by putting the rear on jack stands and "running" it up to 45 mph or so....no vibes. I REMOVED the front shaft to check the u-joints as I could neither see or feel anything wrong with them. Onced removed, it was obvious that one joint on the front of the shaft was froze...

Took the shaft to my mechanic....$30 later no vibes.

Regarding the 242 concerns...I'm running a 242 with the LP D30 in front, at 3" of lift, no problems.

 

[ChuckstrPT]

No one suggested motor mounts or trans mounts?
My ol' 88 (stocker on 30's) first needed a trans mount, vibe fixed.
Vibe came again, worse. Shook the dash, mirrors and steering wheel. Replaced the motor mounts after having it looked at, vibe fixed.
Worth checking...

That would certainly explain the correlation to the gas pedal :sunshine:

 

[Eagle]

Yeah, I replaced the rear driveshaft with a Tom Woods CV style one. And the vibration is constant as long as I'm on the gas. It goes completely away when I let off the gas. I can feel the vibes pretty much everywhere, but I can SEE the steering wheel shake... that should tell you how bad it is. The dash, the seat, the center console, it all vibrates.

Driveline vibrations, especially from the rear driveshaft/axle, do not make the steering wheel shake. Your problem appears to be in the front end. And describing the steering wheel as shaking makes me wonder if what you have is a "vibration," or something of lower frequency and higher amplitude. I have never encountered anything I'd consider a "vibration" that could cause the steering wheel to shake.

 

[MoonShadow127]

Alright... well... here's an update. The weather got up to the 40's today, so I decided to bundle up and go wrench on it for a while... see if I could figure out something the mechanics couldn't.

I started by removing the front driveshaft per all of your recommendations. I drove around town for a while, and the vibes were still there. In the steering wheel and everything. So I greased up the slipjoint, double checked the yokes, and put the front shaft back in.

Then I took the rear shaft out. Put it in 4WD and drove around town a bit. No vibes at all. Intresting. So I went back and inspected the rear driveshaft... I couldn't find any bad U-Joints either. All of them had grease, and none of them had any play in them. It's a Tom Woods HD driveshaft, and the ball in the middle of the double-cardon joint looked a tad dry but made no noise and moved fluidly. I put some more grease on that as well. When I checked the yokes, I found that I could tighten the transfer case yoke about a 1/8th of a turn. Odd. But it wasn't enough that I would think could cause a vibration, and I couldn't find anything really wrong, so I put the rear shaft back in.

So I took it for another test drive, and the vibes are now HALF of what they were before... which basicly only confuses me further. I didn't really do anything but grease things up and tighten the rear transfer case yoke a TINY bit. I hope this tells you all something, because I'm at a total loss now...

Oh, and the motor mounts are fine. I can push up on the transfer case and it wiggles a bit on the crossmember mount, but not much at all. I don't know how much play is suppose to be in it... I never really paid attention.