I got a clunk noise when starting off in 1st. - JeepForum.com
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post #1 of 32 Old 03-25-2021, 06:05 PM Thread Starter
cas6969
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I got a clunk noise when starting off in 1st.

Okay now, I've been on enough forums of various types to know I don't expect anyone to diagnose my vehicle over the internet. But like everything else, there are often common issues with things, "yeah, they all do that when the woolygiger goes bad".

It used to do it once in a while, now doing it more often than not. When I start of in first, after some forward motion I get a low toned muffled clunk noise you can feel in the floor boards. If I come to a "rolling stop", (you know, not fully stopping) then put it int 1st and go, it doesn't do it. Only a dead stop. I've had a couple theories, none of which have panned out. (thought it might be my spare tire/tail gate, thought it was the gas tank which wasn't strapped down in the pan, thought it could be a shock mount that was tearing off)

Motor mounts seem good, replaced the trans and torque mounts last summer. Haven't had a chance to look around in the front end too much, nothing horribly obvious though while shaking the front end while doing brakes.

So I figured it couldn't hurt anything to throw it out there , just in case there are known common issues to check.


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post #2 of 32 Old 03-25-2021, 06:39 PM
shaggyjim
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I had a clunk that took forever to find and mostly happened after a full stop and it was the 9/16 bolts on the leaf spring had worn out the hole on the frame side spring hanger.
I have broken some spring retaining bolts under the axle pad and got some shifting of the axle but I dont remember in clunking.
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post #3 of 32 Old 03-25-2021, 08:12 PM
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a few possible causes:

1. Trans mission mount and/or motor mounts. If you still have the torque bolt on your transmission mount, check that first.
2. U-Joints on your driveshafts.
3. check your skid plate bolts.

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post #4 of 32 Old 03-26-2021, 05:54 AM Thread Starter
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shaggyjim... I will look into it when I have the rear wheels off next week. One of my initial thought was it was something that was happen with some minor wracking at the rear. Maybe I can find some signs of things shifting back there.

Luuca I've dealt with oodles of bad U joints over the years and this doesn't make any of the normal sounds when they start to go. Plus I don't think it does it soon enough. There's no visible play in them, but I have thought about changing them for the heck of it.
Trans pan is tight, mount and torque mount are new. Sadly I don't know if it made the noise before I changed them, as I only drove it once or twice and it basically had no exhaust, so you couldn't hear anything. First thing I did was drop the pan to replace the front piece of exhaust and found the trans mount was mush. I use to wonder if it was just the torque mount doing it's thing, but I think it's getting louder and certainly more frequent.

I use to swear it was in the rear, why I thought it was the tire or the tank. Now I'm feeling it in my feet more and starting to think it's up front.

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Last edited by cas6969; 03-26-2021 at 02:02 PM.
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post #5 of 32 Old 03-26-2021, 07:59 AM
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Re check that torque mount. Make sure all the washers and bushings are in proper order (there are a lot of them).

That is 75% of the cases producing the symptom you described.

Have you tried sharper turning onto a small incline (like a driveway that elevates from street level) with some extra speed to see if it produces that same sound?

Luca was correct on double checking motor mounts VERY carefully.

~YJOTM MAY '16, JULY '19~


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post #6 of 32 Old 03-26-2021, 08:19 AM
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I actually have not had any noise from that trans torque arm since I removed it years ago.
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post #7 of 32 Old 03-26-2021, 09:31 AM
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Quote:
Originally Posted by JeeperDon View Post
I actually have not had any noise from that trans torque arm since I removed it years ago.
That's because you have no giant washer attached to a bolt teetering and clunking when the washer contacts the skid lol.

Regardless, for it to move the drivetrain to teeter that easily... another mount somewhere else (as Luuca suggested, usually motor mounts) have to be worn and weak. My jeep came with this clunk.

Torque arm bolt bent to ****. Changed it out. Same issue. Trans mount was perfect (and still is - thank God for bad transmission leaks never addressed by PO's eh?). Motor mounts were both shot.

Any take off, any turn with speed... clunk.

Also Don, you designed a crazy functional design for a skid plate - cross member - trans mount

~YJOTM MAY '16, JULY '19~


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post #8 of 32 Old 03-26-2021, 12:39 PM
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I would also double check u-bolts and make sure you haven't sheared a centering pin, but I'd think you'd still get the noise on rolling starts or even heavy acceleration.

It's things like this that make me want a GoPro to stick up under places to try and see what's happening.

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post #9 of 32 Old 03-26-2021, 01:58 PM Thread Starter
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(Torque mount) It's very possible. I cut the old one off, because I didn't quite understand how it was made... so I couldn't get it to come apart. After I did I went "Oh yeah, now I see why." Then everyone was out of stock on the bolt, so it was a couple weeks later when I finally got to put the new one on, going by memory of how the parts were arranged. It certainly could be wrong.

Need to find a good diagram online now...... Should be mounted solid to the pan, but loose to the trans bracket. Only rubber/polly touching the bracket, no?


Other things soon to be eliminated, I have new front shocks to put on.

I currently have ONE rear shock, and the other day I learned it has started to empty itself. (if that's the source, the new leak could be why it's getting worse) Going to start on the frame and missing mount this weekend. Going to do needed and preventive frame repair and change both upper shock mounts, with new shocks to follow obviously. While she's up in the air and I spend a few days under it, I will eyeball as much of the spring situation as I can.

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Last edited by cas6969; 03-26-2021 at 02:17 PM.
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post #10 of 32 Old 03-26-2021, 04:14 PM
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Pretty funny because my Jeep JUST started doing the exact same thing.

I'm replacing the transmission and motor mounts here pretty soon. If it still does it I'll start checking other things and report back.

The 4th 5-seater YJ in the world.
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post #11 of 32 Old 03-26-2021, 04:56 PM
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Do you still have your trac bars?
It could be one of the mounts are loose or maybe not attached anymore.
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post #12 of 32 Old 03-26-2021, 05:25 PM Thread Starter
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Quote:
Originally Posted by TSEJEEPERS View Post
Do you still have your trac bars?
It could be one of the mounts are loose or maybe not attached anymore.
Since there was still a little daylight, I decided to go outside and see since I wasn't sure what the answer was. I knew the rear one is long gone, wasn't sure what's doing up front. So I'm laying under the front of the Jeep, grabbing things, yanking on things (shocks crumbling in my hands lol) and I look back at the tranny pan and I see a bolt, and a washer and maybe a 1/2" gap between them. "What the...?" Much to my disbelief and yet delight, the damn torque mount bolt had come loose and was working it's way off.

Tightened it back up. Fingers crossed, off to the grocery store and a test drive.
Either way, it gets some loctite tomorrow.

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post #13 of 32 Old 03-26-2021, 05:41 PM
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to be clear.

That torque arm is not supposed to be tight tight at all. There is a loosey goosey fit on that item.

~YJOTM MAY '16, JULY '19~


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post #14 of 32 Old 03-26-2021, 05:46 PM
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Quote:
Originally Posted by bruinjeeper View Post
to be clear.

That torque arm is not supposed to be tight tight at all. There is a loosey goosey fit on that item.
Yeah, there's at least 1/2" of play in it at all times. In fact, if it's the original torque bolt, you can't actually "tighten" it as the center of the bolt isn't threaded.

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post #15 of 32 Old 03-26-2021, 06:05 PM
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This may be totally incorrect, but I had a clunking sound up front for a while. It was my bearings, which sucked because they're sealed, lol. Was only 1, but I replaced both.

It wouldnt happen all the time, and honestly I barely noticed it, sometimes would rattle at about 45 MPH, then smooth out sometimes. I thought "this mist be that 'death wobble'", lol. Nope, still havent seen that happen, knock on wood. And only clunk at hard turns. Sometimes from taking off as well, but not all the time. It seems that they can kinda "settle" in and therefore problem can "dissapear". I could totally be wrong in this, so take it with a grain of salt.

I think it's easy to check though. Jack it up and jiggle wheel. Easy check, right?
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