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Unread 06-12-2013, 09:17 PM   #1
ChirleyUJest
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2002 KJ Liberty 
 
Join Date: Jun 2013
Location: Crescent City, CA
Posts: 3
Help with rear end problem lol Got me stumped!

My first thread but love this forum! Ok first of all I am female and don't work on my Jeep myself. I can change a tire and change the oil, other than that please use small words. The problem: After I drive about an hour, when first accelerating either in forward or reverse, and especially when turning, I have a grinding sound that is quite loud, I can hear it with the windows up. It is not a clunking but sounds sort of like metal shearing on metal but not squeaking at all - its a deeper grinding sound. It appears to be just inside the rear wheels, underneath the Jeep. I have had 5 different mechanics look at it including a dealer. What I have fixed so far: U joints. Rear differential upper control arm and ball joint. Drive shaft (it went out a while ago and is new but I did drive about 9 months without it.) The mechanics say my shocks, brakes, tranny, differential, etc are fine - they cannot find the problem. I will be driving cross country soon and I am worried about this! Any ideas? Ball bearings? Closer look at the disc brakes? Also, if it helps, I was pulling a 20 foot RV and the noise was louder (more strain?) and the wheels were seen to "slip" a few times. Any ideas would help! Thanks!

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Unread 06-13-2013, 04:53 AM   #2
Billwill
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2002 KJ Liberty 
 
Join Date: Jul 2007
Location: South Africa
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Quote:
Originally Posted by ChirleyUJest View Post
My first thread but love this forum! Ok first of all I am female and don't work on my Jeep myself. I can change a tire and change the oil, other than that please use small words. The problem: After I drive about an hour, when first accelerating either in forward or reverse, and especially when turning, I have a grinding sound that is quite loud, I can hear it with the windows up. It is not a clunking but sounds sort of like metal shearing on metal but not squeaking at all - its a deeper grinding sound. It appears to be just inside the rear wheels, underneath the Jeep. I have had 5 different mechanics look at it including a dealer. What I have fixed so far: U joints. Rear differential upper control arm and ball joint. Drive shaft (it went out a while ago and is new but I did drive about 9 months without it.) The mechanics say my shocks, brakes, tranny, differential, etc are fine - they cannot find the problem. I will be driving cross country soon and I am worried about this! Any ideas? Ball bearings? Closer look at the disc brakes? Also, if it helps, I was pulling a 20 foot RV and the noise was louder (more strain?) and the wheels were seen to "slip" a few times. Any ideas would help! Thanks!
Stupid question but does your Jeep perhaps have the "Trac Lock" rear diff that some KJs...like mine ...have?

This is a form of Limited Slip Differential (LSD) that must have the correct Mopar friction additive added to the rear diff or you can get noises like that.

Ask your "mechanics" to check if you have the Trac Lock....there should be a tag on the rear axle stating if it is there.

Secondly, does your Jeep have the cheaper "Command Track" 4X4 system or the better "Select Track" 4X4 system.
The Command Track has a selection for "2 wheel drive", "4 wheel part time High" and "4 wheel part time Lo".

The Select Track also has the selection of "4 wheel Full time"

If your jeep...like mine...has the Command Track transfer box without "Full Time 4X4" then you can only engage 4 wheel drive...Hi or Lo....on extremely slippery roads and only at a low speed and for short distances or you can get these noises and destroy the Transfer case.

Check your Owners' manual located in the glove box for more information.
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Unread 06-13-2013, 06:30 PM   #3
TwoBobsKJ
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Join Date: May 2011
Location: Northern, OH
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Also check the CV joint at the transfer case end of the front driveshaft. Sadly, even mechanics at dealerships skip right over that CV...

It is right under the driver's seat so its noises sound like they could be coming from the rear axle or even the front wheels. It's easy to check - have your mechanic lift it up, shine a flashlight at the transfer case end of the front driveshaft and look for torn or missing rubber boot around the joint. Most likely it's torn or missing.

If it's bad, DO NOT replace the entire driveshaft even though the mechanic will say you need to. Their suppliers typically don't sell just that CV - they sell the entire shaft. However, you can purchase the CV joint for about $60 with shipping from driveshaftparts.com. Many of us have gone this route and its been fine - I replaced mine in about 45 minutes (took a little longer cuz I painted the driveshaft black!) so your mechanic should have no problem.

If the CV joint is fine...then I just got a lot of practice typing on my phone ;-)

Bob

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Unread 06-13-2013, 06:35 PM   #4
ChirleyUJest
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2002 KJ Liberty 
 
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Hey Billwill, thanks for your response, very helpful! So today I drove the jeep for an hour out on the freeway, headed into town, the noise was there, very loud and scary when we pulled into the mechanics-so much so that I stopped driving it...he couldnt come out right away but about 3 min later came out, got in the jeep, and NO FREAKING NOISE!!! We drove it around town and NOTHING! How does it go from making horrible noises to nothing in the space of 3 minutes??? The front right wheel "clunked/slipped" once when turning left (which was a NEW spot!!) and thats it. Put in 4WD for about a mile then out again, no issues. Soooo--- tomorrow the mechanic is going to change fluids in front/rear differential and tranny. My son is going to drive it around another hour or two before taking it in. Any suggestions?? I am completely frustrated! I read the mechanic your reply. He thinks fluids is a good next step. He has a Jeep also, seems like a knowledgeable guy. I do believe I have the trac lock and command track systems. Any more feedback? Thanks so much! Have to drive the thing from CA to AK next week and seriously doubting at this point that I can safely do that.
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Unread 06-14-2013, 01:45 AM   #5
Billwill
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2002 KJ Liberty 
 
Join Date: Jul 2007
Location: South Africa
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Quote:
Originally Posted by ChirleyUJest View Post
Hey Billwill, thanks for your response, very helpful! So today I drove the jeep for an hour out on the freeway, headed into town, the noise was there, very loud and scary when we pulled into the mechanics-so much so that I stopped driving it...he couldnt come out right away but about 3 min later came out, got in the jeep, and NO FREAKING NOISE!!! We drove it around town and NOTHING! How does it go from making horrible noises to nothing in the space of 3 minutes??? The front right wheel "clunked/slipped" once when turning left (which was a NEW spot!!) and thats it. Put in 4WD for about a mile then out again, no issues. Soooo--- tomorrow the mechanic is going to change fluids in front/rear differential and tranny. My son is going to drive it around another hour or two before taking it in. Any suggestions?? I am completely frustrated! I read the mechanic your reply. He thinks fluids is a good next step. He has a Jeep also, seems like a knowledgeable guy. I do believe I have the trac lock and command track systems. Any more feedback? Thanks so much! Have to drive the thing from CA to AK next week and seriously doubting at this point that I can safely do that.
If it does have Trac Loc make sure the mechanic first puts in the Mopar friction additive in the rear differential before topping up with the new diff oil. Once the rear diff cover plate is off...only way to drain the oil....you can visibly see if Trac Loc is there!

And if you do also have the Command Track transfer case fitted then it is probably dead by now from too much driving in 4X4 on hard pavement!


Good Luck!
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Unread 06-14-2013, 07:48 PM   #6
ppap
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If the limited slip diff was lacking friction modifier additive, you'd hear a "chatter" when making turns ONLY. The clutch packs in the diff are not engaged when both wheels are spinning at the same rate. Highly doubtful this would be the problem because higher mileage limited slip diffs are so worn that the lack of additive wouldn't matter. Based on your description, the noise happens both when accelerating and turning so the lack of additive is not an issue. A couple things to try the next time you hear the noise: 1. Does the noise change when you apply the brakes? 2. Does the noise change intensity when you shift the weight of the vehicle from right to left? My thinking is it could be an axle bearing, u-joint (driveshaft) or a brake issue, possibly hung caliper or rotor/pad issue. The bearing issue can be diagnosed by raising the vehicle off the ground and listening to the axle housing with a stethoscope while the rear wheels are spinning. The u-joint can be diagnosed by disconnecting the drive shaft and wiggling the joint. The brakes can be visually inspected and calipers manually compressed. Hope this helps.
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Unread 06-14-2013, 08:48 PM   #7
ChirleyUJest
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Location: Crescent City, CA
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Thanks for the replies! Hey Bob, already did exactly what you described with the drive shaft, replaced that CV joint only. Thanks for all the typing though! I had the fluids done today-transmission, transfer case and front/rear differentials. Havent driven it much yet (have to drive an hour before the noise starts) but based on ppap's post, I have a feeling it will still make the noise. So, Ppap, the noise does not get louder with the brakes applied. The noise is present most when stopping and starting, when the jeep is only moving a few mph. The brakes have been inspected a few times-no issues. Drive shaft ok and u joints ok. Thinking its the axle bearing. Questions: when you say weight shift do you mean literally trying to shift the weight while driving by leaning back and forth? (Seems a silly question but the noise only occurs when the vehicle is moving). Also, what am I listening for on the axle housing with the stethescope? Thanks a bunch guys, I feel like I might be getting somewhere. What are your views on it possibly being the wheel bearings?
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Unread 06-16-2013, 05:06 PM   #8
ppap
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When an axle or a wheel bearing is faulty, it becomes more pronounced when more weight is applied to it. Find an isolated road and drive the vehicle at the speed where you hear the noise. Cut the steering wheel hard from side to side to shift the weight from one side to the other. A bad bearing will generally get louder when more weight is applied and become quieter when the weight is reduced. This helps to identify which side has the bad bearing. For example, the right wheel bearing is bad. By shifting the weight of the vehicle the left side, the noise will attenuate. Likewise shifting it to the right will amplify it. You can also think of it as turning so if the noise gets louder when you turn right, it's the left wheel bearing that's bad. Note that this is not always the case. I have seen plenty of wheel bearings that don't follow this logic so I always replace both sides regardless. The stethoscope is used to hear for bearing noise when the vehicle is raised. Obviously make sure the vehicle is properly secured and have someone run the engine in park to around 40mph. Using whatever instrument works, listen to both sides of the housing for a grinding sound. The stethoscope is used to isolate and compare the noises on both sides but i've seen people use screwdrivers and assorted other tools. Note, some bearing noises are not noticable without a load on them so this method may not work. In regards to your Liberty, you don't have "wheel bearings" in the rear as you do in the front. Most likely you have axle and differential bearings but the same diagnostic procedure is used. This is probably not something that you'll be replacing yourself in the driveway but it's certainly possible. Any good service shop will be able to diagnose bearing issues within 15 minutes. The key to all this is being able to actually hear the noise in order to perform a proper diagnosis. Otherwise you are just throwing parts at it.
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