Uh oh... KJ develops first problem

durangotang · **Posted:** Wed Mar 19, 2008 10:25 pm

Uh-oh.... the KJ has an issue that has come up! I'll describe it as best I can and maybe you guys can help me out on what to check.

So I only notice this problem when either starting or stopping. If I am stopped and start going (about 60% of the time) I feel a delayed "thunk" somewhere in the driveline shortly after I push the gas. When stopping, I feel it shortly after I press the brake. Nothing audible and it only happens when I am probably <10mph. Also it does not happen when I shift into drive or reverse. I am in 2wd so the front end isn't a consideration. Shifting is fine. No odd noises or smells. No leaks.

My thoughts:
-Rear end? (no leaks, whines, or anything else)
-"Boomerang" ball joint worn and thunking around due to inertia change in axle?
-Torque converter? (no shudder or anything at other speeds)
-U Joints? (no "clang" or symptoms on shift out of park)
-something else?

The KJ is still under warranty so the dealer will take car of it. I would like to have it diagnosed myself though before they do exploratory surgery.

(and yes... I checked to see if something was rolling around in the cab)

dgeist · **Posted:** Wed Mar 19, 2008 10:32 pm

So, it sounds like it's happening when you change the torque applied to the driveline, so chock the front and jack-stand both rear wheels. See if you can get the noise to manifest itself just turning the wheels manually (if it's in the diff) and possibly by leaving the transfer case in neutral and only lifting and turning one side at a time (if it's in the shaft).

Dan

Christopher · **Posted:** Wed Mar 19, 2008 10:47 pm

At least for me lubing the splines on the rear drive shaft took care of my similar issue. Just a thought.

Chris

durangotang · **Posted:** Wed Mar 19, 2008 11:08 pm

No questioning you at all... just curious what problem lubing the splines would fix. Is this assuming that the "thunk" are the splines sticking as they slide forward and back?

BeepBeepJeepJeep · **Posted:** Wed Mar 19, 2008 11:13 pm

durangotang wrote:

No questioning you at all... just curious what problem lubing the splines would fix. Is this assuming that the "thunk" are the splines sticking as they slide forward and back?

I have limited expierence with things like this, but I'd take a look at your U-joints. When they start to go, they give you a symptom here and a symptom there. If it was in the differential you'd likely have other problems.

Edit: I just reread your post and you said you don't hear anything... Then it's probably not the U-Joints *shrug*

Jeepjeepster · **Posted:** Wed Mar 19, 2008 11:41 pm

Sounds like normal drive-train slack.

My Locker makes it alot worse.

durangotang · **Posted:** Wed Mar 19, 2008 11:44 pm

It just started doing this about 3 days ago so I don't think it's normal....

***just realized that I should check the rear lugnuts **** :shock:

dloc_jeep_KJ · **Posted:** Thu Mar 20, 2008 12:00 am

durangotang wrote:

It just started doing this about 3 days ago so I don't think it's normal....

***just realized that I should check the rear lugnuts **** :shock:

could be the lugnuts. ive dont that before (not on the KJ) when i was younger and that was about what you described. its worth checking for sure.

Christopher · **Posted:** Thu Mar 20, 2008 1:20 pm

The drive shaft was not sliding smothly on the ouput shaft. Thats why I lubed the splines, they were pretty dry actually.

Chris

Christopher · **Posted:** Thu Mar 20, 2008 1:21 pm

As stated the u-joints would be a good thing to check as well. I would hope that they are not bad on a 06. Thats a pretty short life span even for a cheap u-joint.

durangotang · **Posted:** Thu Mar 20, 2008 2:46 pm

So all the lugnuts were tight. I also climbed under the vehicle and couldn't get ANY movement out of the driveshaft so it's pretty tight. Couldn't get it to slide at all to or from the rear end either. "Boomerang" ball joints look good and no movement there. I guess it's time to jack it up and start spinning stuff.

tommudd · **Posted:** Thu Mar 20, 2008 5:01 pm

my u joints were tight as well, but made noise since they were rusted solid!

durangotang · **Posted:** Thu Mar 20, 2008 5:22 pm

similar symptoms or did they do the typical "clang" shifting out of park?

Jeepjeepster · **Posted:** Thu Mar 20, 2008 6:14 pm

If the kj was on an incline at all then you wont be able to move the drive shaft. It should have some play in it if you try to turn it.

Try to turn the front one if you want to see how much slack the drivetrain has(given its in 2wd).

waddy whiteguts · **Posted:** Thu Mar 20, 2008 9:53 pm

Slip yoke is binding. Mine does the same thing once in a while. Pull the driveshaft, grease the splines, not the end, put it back together. Make sure you don't put the driveshaft in upside down or you'll get a vibration.

Marlon_JBT · **Posted:** Thu Apr 10, 2008 9:43 am

I took mine in the shop for this exact same problem. ('06 Sport w/CRD)

Engine Mounts. Might want to tell them to look into it as it took my dealer 2 trips to figure it out and finally fix it.

theBIGbCraig · **Joined:** Sat Sep 22, 2007 12:28 pm **Posts:** 20

?? I just asked this and it was summed up to drivetrain slack. I'm amazed at all the possibilities that are being thrown around, just 2 weeks after i asked THIS SAME QUESTION.

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=31182
OK, i worded it differently. But still.

JNJ-Z · **Posted:** Sun Apr 13, 2008 8:13 pm

mine is doing the same thing right know, and i pin pointed it to the rear drive shaft, up by the spines!! need to take it out and clean it! its all rusted!!!!

durangotang · **Posted:** Fri Apr 25, 2008 1:39 pm

Just wanted to update everybody... I finally got to take care of this problem and after checking EVERYTHING from the back forward I had a loose motor mount. Just tightened it and off I go...good as new

(ok so someone earned an official "I told you so")

theBIGbCraig · **Joined:** Sat Sep 22, 2007 12:28 pm **Posts:** 20

Where is the mount which mount? Mine seems to be getting worse, and I don't have time to take it to the dealer. (actually, i'm busy trying to sell it, which may or may not happen)

Thanks!

Uh oh... KJ develops first problem

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