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Discussion Starter · #1 ·
Searched what I could in the forums but couldn't find anything that sounded similar. When I accelerate I hear a thunk, thunk, thunk that gets faster until I reach 30ish mph when the thunking gets fast enough it is more of a vibration. I can not hear it outside the vehicle and it does not do it when not accelerating. I have opened the door and put my head down to listen while I accelerated but nothing until I close the door and quiet down the cabin noise. It feels like it is coming from below me. I do notice a little play in the drive line when I do a California stop at a stop sign, where it seems like there is a moment that the drive-line has before everything catches up. I have been working through a lot of issues on this car so I have already replaced or checked everything forward of the transfer case. I replaced the front diff because I thought it had too much play and it was leaking. I replaced the front drive shaft because I thought it was the cause of the noise and the old one was pretty rusted up. When I grab either the front or rear drive shafts there is minimal rotational play and no noticeable up-down/left-right play. I haven't removed the rear driveshaft yet. The transmission pulls hard and shifts fine. The engine runs great, idles great, pulls really hard. The rear diff input shaft is leaking a little but I notice no play. The noise has very slowly gotten worse over the past few months. Changed transfer case oil and it was clean. Changed the rear diff oil and it was clean. Could the transfer case be making this noise? Maybe the rear diff radiating the noise forward? How can I test? Thanks for any help, it's driving me nuts!

Replaced so far:
Front L/R hubs
Front L/R cv axles
Front L/R sway links
Ball joints
Upper control arms
Shocks
Front Diff w/ new bushings
Front driveshaft
 

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Sounds like it is probably a u-joint. You may or may not be able to check it with your hand if the drive shaft has a load on it after you stop. Jack up your rear axle with both wheels off the ground. If u-joint bad. should be able to feel by hand then.
 

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Discussion Starter · #3 ·
Sounds like it is probably a u-joint. You may or may not be able to check it with your hand if the drive shaft has a load on it after you stop. Jack up your rear axle with both wheels off the ground. If u-joint bad. should be able to feel by hand then.

I will give that a try this evening. Thank you.
 

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Hoist

Jack up both front and rear of the car with jack stands or put it on a 2 post hoist make sure it is secure and check first by hand and then use the motor with someone else checking/listening, but again MAKE SURE THE XK IS SECURE.

Swanny
 

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Check the front differential isolator bushings. The top bushing on top of the differential housing below the driver side is a known weakness and can cause a lot of clunking when pulling away from a stop or just driving if the isolator is bad enough. If there is a noticeable clunk when engaging drive or reverse this would indicate that this isolator bushing is shot.
 

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Discussion Starter · #6 ·
Check the front differential isolator bushings. The top bushing on top of the differential housing below the driver side is a known weakness and can cause a lot of clunking when pulling away from a stop or just driving if the isolator is bad enough. If there is a noticeable clunk when engaging drive or reverse this would indicate that this isolator bushing is shot.
All new bushings and seals on the front diff. Installed with the replacement front diff.
 

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Discussion Starter · #7 · (Edited)
Sounds like it is probably a u-joint. You may or may not be able to check it with your hand if the drive shaft has a load on it after you stop. Jack up your rear axle with both wheels off the ground. If u-joint bad. should be able to feel by hand then.
I chalked the front tires, put it in neutral and jacked up the rear. I cant see any visible play in either joint on the rear driveshaft. At most I barely noticed an ever so slight movement in the center of the driveshaft where the splines are but that may have been just the plastic housing flexing. There is no grinding or visible play in the propshaft of the rear diff so even though it is leaking it doesn't appear to be loose. The transfer case makes a lot of noise when I rotate the driveshafts back and forth. If I hand rotate the driveshaft it appears to be smooth with no noticeable noise, clicks, or clunks. I did notice that it does not make the repetitive thunk in reverse. I made 2 youtube videos of what I checked last night.

 

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Discussion Starter · #8 ·
Jack up both front and rear of the car with jack stands or put it on a 2 post hoist make sure it is secure and check first by hand and then use the motor with someone else checking/listening, but again MAKE SURE THE XK IS SECURE.

Swanny
I did that once and it didn't appear to make the noise. It seems to only make the noise under a load like when accelerating.
 

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Discussion Starter · #10 ·
Looks like you have a bad drive shaft seal on your rear differential. Did you check your oil level in the differential?
I did. New oil 2 months ago also. Seal def needs replaced but from what I understand that's pretty hard or expensive to do.
 

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Here is the drive train noise I had which ended up being the cv joint on the front driveshaft.

Sent from my LG-D851 using Tapatalk
 

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Discussion Starter · #13 ·
Update to an old post. I haven't messed with the Commander in a bit since I moved to Charlotte and bought a daily driver car. It's time to finish her and start driving daily again. I am purchasing a used low mileage transfer case soon and hopefully getting it swapped early January. Will update if the noise is gone. Anyone from Charlotte with recommendations on a shop that is familiar with these Commanders? I want to get my exhaust manifold bolts fixed soon too so would like to work with a shop that knows what they may be getting into.
 

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Discussion Starter · #14 ·
This is a saga that doesn't want to end. For a recap the noise is a metallic/binding "click-clack" noise (no grinding) that happens with each tire rotation but ONLY when accelerating and appears to come from under the drivers feet or center console area. The harder the acceleration the louder the noise and there is a slight vibration that I think is associated with it. The noise is not RPM or gear dependent. As I accelerate with the transmission shifting and rpm's changing the noise does not change. Above 40 mph it doesn't seem really noticeable because the tires are rotating fast enough and wind noise but I can still feel the vibration when I accelerate. The noise started after the lift and has grown slightly louder over time. At this point I am literally about to attempt an action movie scene where I hang from the bottom of the car while someone accelerates so I can pin-point the noise (not really but I'm definitely frustrated).

Initially I replaced the front CV axles with Cardon Select reman's and when that didn't work I installed a new front driveshaft but it also made no difference. So next I thought maybe transfer case chain or internal bearing/bushing so I swapped the transfer case for one with only 84k miles. The noise persisted un-changed! Next I thought maybe the original 12 year old rear drive shaft had a bad u-joint I couldn't feel so I replaced it with a new steel driveshaft with serviceable u-joints. The noise persists but slightly louder now!! Finally I thought maybe rear diff ring gear issue because two things 1) now that the noise is slightly louder maybe the new steel shaft is resonating noise from the rear diff more than the aluminum and 2) the noise occurs with each tire rotation, not driveshaft rotation. But since I don't have any differential experience I decided to take it to a 4x4 professional for a diagnosis. He blew away my theory and said front CV axles, even though i replaced them 5k miles ago (I told him this but he persisted). Sooooo I went out and bought new not reman front CV's and dug into replacing them along with my LCA's since the bushings were looking a little old. The noise persists but even louder now!!!

The transfer case and front differential changes didn't change the noise level or frequency at all. The only things that have affected the noise (by making it louder) was the rear driveshaft and new front CV axles, otherwise everything I have done hasn't affected the noise at all. At this point the noise is louder than my new Magnaflow exhaust.

So far I have done the following:

2" RR lift w/ Bilstein shocks (21.5 hub center to flare)
1.25" spacers
255/70R17 tires
JBA UCA's
OEM LCA's w/ new bushings
OEM sway bar links
Moog Sway bar bushings
Timkin front L/R hubs
NEW Carquest front L/R CV axles
Low mileage front differential w/ new bushings (Amsoil fluid+mopar additive)
New front driveshaft
Low mileage transfer case (Mopar fluid)
New rear steel driveshaft
Rear differential Amsoil fluid+mopar additive
 

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Man o man...could it be transmission related?
 

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Discussion Starter · #16 ·
Man o man...could it be transmission related?
I don't think so. It doesn't change with engine RPM and it is directly related to the axle tire rotation (1 click/clack per revolution).

On a positive note I think I have isolated the noise to the front passenger hub. I decided that hanging from the bottom of the Jeep wasn't save ;-P so I went out and bought a cheap wifi action camera that I attached really close to different areas of the car. After lots of recording and driving around like a drunk lunatic I finally recorded the noise loud and clear! Bought a new front hub and will be installing this evening. Here is a video of the noise.

 

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thats a great idea. i have a voice recorder and gonna do the same thing this weekend. i have a howling noise 50-70mph that i can not isolate. must be front diff or xfer case as i have replaced everything else!
 

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Check the CV joint in the front drive shaft, that was the cause of a similar noise on my QDII. See if there is lateral play in the shaft.
 

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Discussion Starter · #19 ·
Check the CV joint in the front drive shaft, that was the cause of a similar noise on my QDII. See if there is lateral play in the shaft.
Front drive shaft is new. Noise did not change between old and new drive shafts. Also the video I posted definitely has the noise coming from the front passenger wheel hub area.
 

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Discussion Starter · #20 ·
Front hub was not it!! Sound is still there.

Today I went and tried to get the noise to change, just to get a reaction out of it so I can pinpoint the source. I tightened and loosened both front half shaft nuts at different torques, even as far and backing off 1/4 inch so the splines can slide in and out a little and tightening them to 300+ ft/lbs. Did a lap around my parking garage but the noise didn't change with any combination of loosening or tightening. I even went and popped the passenger half shaft out a little at the differential so the snap ring wasn't holding. My goal was to allow the half shaft to free up some just in case it was to tight or loose for some reason but no change. I even loosened the lower diff bracket so it could shift a little but no change in the noise at all.

At this point I am thinking maybe an issue with my front diff and maybe the noise is loud at the hub because it is resonating down the half shaft to the hub area where it is being amplified.

If someone can pinpoint this I will for ever be indebted to you and you might save a human being from going insane!
 
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