JackJare9455

Mine has sounded like a sewing machine since day 1... Runs like a champ..

cruiser54

Mine all have, too.

HelmuthJ

OK...I have read all the post...my 97 4.0 automatic is making the same sound. I spend an hour under the jeep with a friend. We found a loose bolt, flex plate to torque converter, tight it and checked all the others. My friend who is an X-Army mechanic said it looks like the Torque converter is wobbling and maybe the balance weight has come off. So I am going to pull the trans back...replace the flex plate with new bolts and replace the Torque converter....I pray that this fixes the noise.... if not....I am at loss also. Or am I wasting my money. ????
John J. in SC

mitch500

My jeep makes the same sound as post 13. I've just learned to live with it after trying to chase it down.

HelmuthJ

OK...found the problem. Could not see this just by looking through the inspection plate, I had to pull back the auto transmission and take off the starter ring/ flex plate...cracked for sure.... I am luck the whole thing did not just break away while driving... Now for a new one and back together...thanks to all for helping me.

cruiser54

Well, seems Helmuth stuck with it and found the problem, ignoring the advice of others to ignore the issue.

Should be a lesson here, I guess.

If anyone wants to find and fix some knocking issues and have an auto trans, here's 2 links to help you do so:

https://www.cherokeeforum.com/f51/ho...ocking-125547/

https://www.cherokeeforum.com/f2/fou...emoval-171945/

SantosClaus

Mine sounds the same. I checked the bolts and where tight but loose enough so I removed them and put lock tight. It he holes were good but think I have a full crack around the base but can't fully verify. I have teeth wear in sections of the plate. The noise sounds better but need to replace soon.

FYI. I think the harmonic balancer caused the issue because it just started but the harmonic balancer I think was making a whistle whining sound since I got it. I will replace that first and then the plate.

Turbo X_J

^
Mounting bolt for the starter is loose.

99Justin4.0

Just found this thread. I just bought a pristine 99 WJ with 200,000 miles for $1600.

It makes the exact same noise as post 13. But mine never quiets down. it's at all times.

Runs PERFECT.

I've been worried sick about it, so I rarely drive it. But I've been trying to find the problem. I have a stethoscope, but can't isolate it. One thing I can say is that cylinder 3 (from front) has low compression. I just pulled the flex plate access, but haven't examined the whole thing yet. I'm also gonna do a wet compression check on that cylinder to see if it's a stuck lifter or something else.

Forgot to mention, there are no signs of a cracked head whatsoever.

I will keep posting my findings on the 4.0 mystery knock.

99Justin4.0

Mine was a broken piston skirt. So everyone calling it the "Mystery Knock" that haven't pulled their pan, that's my guess.

Mine sounded just like post 13, and you could hear it when it revved up, got hot, and all the time. Never went away. And it was consistent, clearly something happening once or twice a rotation.

VImototv Nick Montes

Mine sounds like that, some times when cold, there is no noise, and if i throttle to 1500rpm sound disapears. I think is not piston or conecting rod because i drove it for about 10.000 kms since one year ago every day and noise has not increased. One thing my water pump leaked coolant 4 days ago

bryzmon

I'm 210,000 miles, runs great but have same knock (Post # 13 in video,). It's lower, not lifters. Checked flex plate and pistons, both look ok. Used a stethoscope and it's right in that area.

blazer 2008

If you hit the flex plate lightly with a wrench it will ting like a bell and it,s not cracked, if it thuds then is cracked . I was told that by a tranny shop. Didn,t read all the posts

Lifted_BlueXJ

My 98 with 223, just replaced the harmonic balancer and the knock just started like in post 13. It’s been making the noise for couple of days now. It goes away with throttle, you don’t hear it then you come to a stop you hear it, seems like it does it when it wants too. I haven’t checked the bolts on the flex yet. I’ve had the Jeep for 2 years and it’s always been quiet until I replaced the balancer and now the knock. I wouldn’t think it could the flex because I had the tranny rebuilt a year ago!!! I’ve been running just 10w30 should i run a heavier weight?

cruiser54

check the flexplate bolts.