2004 KJ Rear End Thump - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Liberty Forums > KJ Liberty Forum > 2004 KJ Rear End Thump

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineSteering and more from Ruffstuff!Even Better Heim Pricing! From Ruffstuff

Reply
Unread 11-11-2010, 06:05 PM   #1
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
2004 KJ Rear End Thump

Hi-

I recently purchased my 04 KJ with 97K on it and have discovered a problem that I could use some opinions on. I have noticed when I accelerated quickly off a slow roll (ie punch it), I get a loud thump, thud, slam kind of noise and feel from what appears to be the rear end. I also seem to notice it mostly when doing so starting to turn.

For example, I am leaving our condo complex to the main road rolling slowly, I see no traffic and hit the gas to turn out and get the thud.

It however only happens under this condition. Slow accelerations are fine.

Any ideas on what it could be? I am concerned it might be an issue with the rear axle. A local shop suggested control arm bushings. Thoughts?

Any help is much appreciated.

lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-12-2010, 05:10 AM   #2
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
Anyone??
lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-12-2010, 10:05 PM   #3
LibertyTC
Registered User
2004 KJ Liberty 
 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
Anytime I hear the word thump bang clunk or otherwise, I normally think of u joints related on driveshafts or a Trac-lok / diff in trouble. The GL5 fluid should be changed out frequently so pulling the cover and inspecting is a good idea as well
I would get this up on a hoist inspect the jeep.
I have had to replace my rear lower control arm bushings, where the diff was shifting a bit, the jeep at highway speed would push left when stepped on gas, and when gas released to coast, would drift right, with no clunks etc.
I have also heard that the rear parking brake drum can cause this effect, so while taking off lightly apply parking brake and see if it stops.
LibertyTC is offline   Reply With Quote Quick reply to this message
Unread 11-14-2010, 08:15 AM   #4
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
Well I took it to a shop and hopefully got a proper diagnosis. The guy was a former Chrysler dealer mechanic who seemed familiar with the KJs.

We went for a ride and he first thought it was a rear end posi problem. He put it up on the lift and found out it didn't have posi and upon further inspection found the front prop shaft CV boot torn with a cracked shaft. I could have swore the problem was in the rear end but maybe it was traveling through the driveline.

He said the front shaft spins in 2wd because it never disengages from the front diff.

So my plan is to remove the shaft and test drive it for the thump without it in place. Either way I guess it's time to find a replacement.

Is it reasonable to think this is where the thump is coming from?
lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-14-2010, 08:18 AM   #5
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
Also as an FYI, I had the 4WD and transmission fluid service done yesterday. I also did rear pads, rotors, parking brake shoes and hardware the weekend prior.
lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-14-2010, 07:14 PM   #6
LibertyTC
Registered User
2004 KJ Liberty 
 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
How many times have I heard about noises that are at the opposite end of where you think they are coming from. Some stuff is hard to note it's exact location, without careful inspections.
"He said the front shaft spins in 2wd because it never disengages from the front diff." TRUE!!!
Good idea to remove it and ensure there is nothing else to be replaced.
LibertyTC is offline   Reply With Quote Quick reply to this message
Unread 11-15-2010, 08:03 PM   #7
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
It looks like my intuition was right. I removed the front drive shaft yesterday. Although it does have a torn CV boot on the t-case side, I could see any cracking on the shaft at all.

I've been driving it with the front shaft removed and I still have the same problem. So I guess it wasn't the culprit.

So any other suggestions? Do I need to get it to a rear end shop to get looked at? Could it need a rear end rebuild of some kind? What are typical costs?

It's hard to reproduce as it's intermittent, but I seem to notice it most when turning out from a lot onto a main road with moderate acceleration. It definitely feels like a "slam". I never get it with light acceleration at all.

I'm stumped!
lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-15-2010, 08:22 PM   #8
LibertyTC
Registered User
2004 KJ Liberty 
 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
Pull the rear dif cover and have a look in there.....did you have"the Mechanic" check your u-joints ,shock bolts tight?
LibertyTC is offline   Reply With Quote Quick reply to this message
Unread 11-15-2010, 09:06 PM   #9
lilngineer
Registered User
2004 KJ Liberty 
 
Join Date: Oct 2007
Location: Chesterfield Twp, MI, MI
Posts: 62
What might be the problem in the rear diff?

BTW- I am mostly the mechanic on this one. The shop just took a free look at it for me on Saturday. (I also quickly took a look at the front drive shaft while on the lift. I asked him at that time if ge noticed anything else and all he commented on was the front brakes and a slight rear main leak.

I also asked about u-joints but he said they would be vibrating like crazy if they were the problem.
lilngineer is offline   Reply With Quote Quick reply to this message
Unread 11-15-2010, 09:41 PM   #10
LibertyTC
Registered User
2004 KJ Liberty 
 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
I would seriously consider asking a dealership if they would charge you to have a service adviser do a ride along to help diagnose this problem. They might even throw it on a lift for you and exactly identify the problem though a proper inspection.
LibertyTC is offline   Reply With Quote Quick reply to this message
Unread 11-18-2010, 09:10 PM   #11
TexAcoon
Registered User
1990 YJ Wrangler 
 
Join Date: Oct 2008
Location: Lincoln, Nebraska
Posts: 40
From what you stated sounds like the same thing I had.

Replaced both rear shocks and it took care of the clunk...

Might look into that ..
TexAcoon is offline   Reply With Quote Quick reply to this message
Unread 12-11-2010, 03:00 PM   #12
davegt
Registered User
1983 CJ5 
 
Join Date: Jul 2008
Location: canada
Posts: 380
rear control arm bushings stopped the same noise on mj jeep. the control arm holds the whole axel in place any movement in the bushings and the axel will move. i thought my tranny was slipping or my rear end was
shot. Also the you may as well replace the whole arm if the bushings are gone. the control arm doesnt seem to made very well. i have only 111,000 k on mine and the metal was bending very easy from rot and rust when pressing the bushings out and while putting the new ones in. Im looking for a new control arm now and it seems when you buy the arm u grt the ball joint and bushings for around $150-200
davegt is offline   Reply With Quote Quick reply to this message
Unread 12-20-2010, 04:33 PM   #13
waywardtravel
Registered User
2006 KJ Liberty 
 
Join Date: Dec 2010
Location: Panama Country and, az
Posts: 76
Maybe your lucky and someone installed a detroit locker before you.
waywardtravel is offline   Reply With Quote Quick reply to this message
Unread 02-01-2011, 12:13 PM   #14
jimymc
Registered User
2003 KJ Liberty 
 
Join Date: Dec 2009
Location: Jax, FL
Posts: 68
What you may be experiencing is takeup of the slop in the drive train. Sounds like you are rolling in a downhill direction when you accelerate and all the rolling force is backed up in the drive train. The drivetrain is being driven by the wheels. When you accelerate the force from the engine is in the forward direction and any slop in the drivetrain is accentuated when it catches. Just the slight incline of a driveway into the road is enough to do this. It you don't hear this sound when accelerating uphill I would suspect this is the culprit. Unless it is really bad, I wouldn't worry about it. Most high-mileage vehicles will do this. I've got 128,000 miles on my Libby and it will do it. Just take it easy on the first part of the acceleration when you are starting out downhill.
jimymc is offline   Reply With Quote Quick reply to this message
Unread 02-01-2011, 02:14 PM   #15
brendanc
Registered User
2002 KJ Liberty 
 
Join Date: Jul 2009
Location: Alexandria, VA
Posts: 322
Quote:
Originally Posted by jimymc View Post
What you may be experiencing is takeup of the slop in the drive train. Sounds like you are rolling in a downhill direction when you accelerate and all the rolling force is backed up in the drive train. The drivetrain is being driven by the wheels. When you accelerate the force from the engine is in the forward direction and any slop in the drivetrain is accentuated when it catches. Just the slight incline of a driveway into the road is enough to do this. It you don't hear this sound when accelerating uphill I would suspect this is the culprit. Unless it is really bad, I wouldn't worry about it. Most high-mileage vehicles will do this. I've got 128,000 miles on my Libby and it will do it. Just take it easy on the first part of the acceleration when you are starting out downhill.
You can compensate for this by increasing the RPMs in neutral/clutch depressed to match the speed. Then the "catch" doesn't occur.
brendanc is offline   Reply With Quote Quick reply to this message
Reply

Tags
kj , rear , thump

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.