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Transmission knocking sound that goes away when clutch is depressed

ChiefTJ

New Member
Joined
Nov 4, 2019
Messages
3
Location
Mahtomedi, Minnesota
I have an '02 X with 43,000 miles on it. For some time now it has been making a knocking sound when I'm not in motion or in gear. I can only describe it as a diesel engine knocking. When the clutch is out the sound is extremely noticeable but when the clutch is pushed in the sound stops. This only happens after long periods of driving (usually about 30 minutes of constant driving). I've had the clutch kit replaced a few times already, both at roughly 42,000 miles, to try to alleviate the sound but it hasn't worked. Has anyone had or heard of this problem before?
 

reddvltj

TJ Enthusiast
Supporting Member
Joined
Apr 15, 2019
Messages
556
Location
Challis, ID
I have an '02 X with 43,000 miles on it. For some time now it has been making a knocking sound when I'm not in motion or in gear. I can only describe it as a diesel engine knocking. When the clutch is out the sound is extremely noticeable but when the clutch is pushed in the sound stops. This only happens after long periods of driving (usually about 30 minutes of constant driving). I've had the clutch kit replaced a few times already, both at roughly 42,000 miles, to try to alleviate the sound but it hasn't worked. Has anyone had or heard of this problem before?
Have you replaced the gear oil in your trans yet?
 
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ChiefTJ

ChiefTJ

New Member
Joined
Nov 4, 2019
Messages
3
Location
Mahtomedi, Minnesota
I wish I was able to post a video. It sounds pretty bad, I think I'm going to run it until it dies. The transmission fluid should be fine, I just brought it into the shop because of a burning smell. Turns out the previous mechanic had overfilled it somehow... But the sound has been around longer than that so I don't think it's because of the overfilling.
 

reddvltj

TJ Enthusiast
Supporting Member
Joined
Apr 15, 2019
Messages
556
Location
Challis, ID
I wish I was able to post a video. It sounds pretty bad, I think I'm going to run it until it dies. The transmission fluid should be fine, I just brought it into the shop because of a burning smell. Turns out the previous mechanic had overfilled it somehow... But the sound has been around longer than that so I don't think it's because of the overfilling.
It is entirely possible that they used an inadequate gear oil in the transmission. When I first got my '00 in February the trans was pretty loud when just sitting and idling with the clutch out in neutral. After reading about what should be used I did a drain and fill with the mopar gear oil and it cut the sound in half.
 
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ChiefTJ

ChiefTJ

New Member
Joined
Nov 4, 2019
Messages
3
Location
Mahtomedi, Minnesota
Sounds like I should change the oil in the transmission. When I get the chance I'll switch it out, hopefully it's not a bearing like Chris said but it's entirely possible. Thank you to everyone that replied!
 
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bromel

TJ Enthusiast
Joined
Oct 11, 2018
Messages
299
Location
Montauk, NY
The NV3550 is notorious for making a "marbles in a can" noise in neutral with the clutch out. It's just the engine turning the input shaft. They call it gear rollover noise. Most cars have much better soundproofing, so you don't hear it. The TJ has nothing. Redline MTL does quiet it down somewhat, but you ultimately have to learn to live with the noise.
 

rubigold

Member
Supporting Member
Joined
Mar 22, 2019
Messages
63
Location
Connecticut
yup same thing here. changed to redline mtl and its definitely quieter. i feel like i've read that a lot of people prefer the ax15 over the nv3550
 
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