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post #1 of (permalink) Old 09-13-2003, 12:19 AM
mikeinta
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What\'s that thumping noise?

I just started noticing a thumping noise underneath my rig after I back out of my driveway and start moving forward (up a slight hill). It's underneath seeminly coming from between the two seats towards the dash. It happens if I accelerate quickly, but not if i just ease the pedal.

Thoughts? What could this be?

Thanks as always.
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post #2 of (permalink) Old 09-13-2003, 12:23 AM
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Re: What\'s that thumping noise?

Broken or squashed tranny mount?
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post #3 of (permalink) Old 09-13-2003, 12:29 AM
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Re: What\'s that thumping noise?

Do you have a cat? [img]images/graemlins/grin.gif[/img] OK that was poor taste, but you might want to check you u-joints.
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post #4 of (permalink) Old 09-13-2003, 12:53 AM
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Re: What\'s that thumping noise?

Does it ever happen on the street under any other circumstances? I'd guess broken tranny mount myself. Take a look under it to see if you can find any marks to see if the yolks are hitting anything.
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post #5 of (permalink) Old 09-13-2003, 01:00 AM
 
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Re: What\'s that thumping noise?

I can't quite remember, how is it that you flush out a cat??? SOMEBODY on this BBS has to know....

That was a *good* thread!
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post #6 of (permalink) Old 09-13-2003, 01:25 AM
 
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Re: What\'s that thumping noise?

My '95 fullsize Bronco makes a double thumping noise under initial acceleration, and when coming to too rapid of a stop. Did some research (involved lying under the bronco with it on jackstands and having it put in forward and reverse multiple times with the brakes held--the clunking was distinct, and we slowly isolated it to the T-case...you could feel the thump heavily when your hand was on the case) and found the chain in the T-case is simply stretched and has some slack in it. I'll probably drop a new chain or swing out the case this winter.

I'd check U-joints and mounts first.
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post #7 of (permalink) Old 09-13-2003, 02:10 PM
mikeinta
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Re: What\'s that thumping noise?

Many thanks. I'll check the transmission mounts.

By the way, the cat's fine, just a few grease marks...
post #8 of (permalink) Old 09-13-2003, 04:41 PM
 
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Re: What\'s that thumping noise?

I had something similar on my '90 YJ, and under similar driving conditions...After replacing the motor mounts and driveshaft ujoints (why someone would install a non-greasable ujoint is beyond me - the needle bearings were reduced to dust), it was still making the sound...I had the muffler, cat and all hangers replaced last week because all the joints were loose and the hangers were barely functional, and voila! The noise is gone. Your TJ is newer and has to be in better shape than mine, but the exhaust is something else to check...

Cheers...
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