Ungodly Vibration when on highway in neutral

[RLVRSK]

So recently I've noticed a horrible vibration at 55+ whenever my Jeep (it's a 6 speed LJ rubi) is not in gear. I also notice a slight pulse/vibration being transmitted through the clutch pedal when pushing or releasing it. Also, say I'm cruising in 5th (or any gear at high speed) and i leave it in gear and let off the gas, there's a sort of thud/vibration that instantly goes away as soon as it starts to engine brake. There's nothing leaking out of anywhere on the Jeep. I have 39k miles (some are very hard miles) and it's the original clutch. Any ideas? oh, and it's not the Ujoints in the rear drive train. I just replaced them about 5k ago, and there is no wobble in the shaft anywhere.

On a related note: It seems that if I put it in 4HI and drive it around for a bit, and then take it out of 4HI and drive it a little more the problem goes away, or at least lessens. Then it comes back :\

any insight would be very helpful. I need to drive home from VT to MA for thanksgiving break. Thanks!

[JamesTree]

You might want to check the transmission mount, it bolts on to the skid plate. I had that issue on the ride home from a Baystate run last year, the jeep rode pretty rough on the ride home. The symptoms were kinda similar.

[ZAEDOCK]

39K on a Jeep clutch is nothing. Even used hard they last much longer.


Need more info though:

Lift? Tires? Mods? Double cardan rear driveshaft?


Hate to say it, but you're symptoms point to a rear u-joint. A contaminated joint can be toasted in a matter of miles.
Could be a loose pinion in the rear end too. You're going to have to check all moving driveline parts.

[RLVRSK]

After looking at it in the day light I've determined it's the front driveshaft. It's a CV with double ujoint at the tcase. the shaft has a TON of play where the two pieces meet. the 4 inches of lift with 35's and hard wheeling must have finally caught up w me. fun fun fun.

[Kurt]

I'd highly recommend you pull the front DS out until you can get it fixed.
The CV can lock up and grenade the tcase

[Hoodoo Man]

Or just stay out of neutral on the highway....

[RLVRSK]

Makes sense. That was gonna be my next question. The tcase isnt gonna spew fluid if i pull the DS right? just want to be sure, never had to disconnect the front like this. If not, sounds like a plan any recommendations for a new DS so this doesn't happen for a while? or am I just gonna need to deal with it. Search Hobicon in the jeep registry, has all my specs. Thanks again guys!

[Kurt]

Nope the tcase won't spew any fluid when the front DS is removed.

Most likely the centering assembly in the front DS CV is what went bad.
This...


They usually wear out due to a lack of lube.
It can be purchased from Dennys Driveshaft at: http://www.dennysdriveshaft.com/
for about $45. More if you want a more complete kit with new u-joints, etc.
Great place with quick shipping.
I as well as others in BSJ been very please with their service.

If you know how to replace a u-joint then you can easily rebuild the front DS yourself and save a chunk of change.

[Hoodoo Man]

X2 on Dennys... They are in Albany and things get here very quick...

[ZAEDOCK]

Definitely rebuild. No need to replace.

[Kurt]

X2 on Dennys... They are in Albany and things get here very quick...

Actually they are in Kenmore, NY

They are a few blocks from where I grew up as a kid

[ZAEDOCK]

I went to Denny's for breakfast.

The food is good and has lots of iron.

[RLVRSK]

UPDATE:
Front Drive Shaft is now removed. Still getting vibrations around 40-50+. Also getting a squeek when shifting and the clutch pedal is about 1/3rd pushed down. Vibrations still only in neutral. Been reading up on the angry sparrow crap, but nothing says anything about violent shakes. Literally the whole Jeep (gotta be coming from the back) is like I'm on a highway rumble strip. Could be the ujoints in the rear near the tcase? Because I can grab the shaft and try to shake it, but get no play at all.
No idea at this point...
Thanks all!

[RLVRSK]

Nope the tcase won't spew any fluid when the front DS is removed.

Most likely the centering assembly in the front DS CV is what went bad.
This...


They usually wear out due to a lack of lube.
It can be purchased from Dennys Driveshaft at: http://www.dennysdriveshaft.com/
for about $45. More if you want a more complete kit with new u-joints, etc.
Great place with quick shipping.
I as well as others in BSJ been very please with their service.

If you know how to replace a u-joint then you can easily rebuild the front DS yourself and save a chunk of change.

This seems like it makes the most sense. Going to inspect tomorrow in the light.

[ZAEDOCK]

Pull the shaft, then you will know for sure. Unless it's really toast, you won't be able to shake it by hand very easily.