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  #1  
Old June 3rd, 2007, 16:53
macrat123 macrat123 is offline
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Tap gas pedal = thump / clunk

Hello, I have searched but i couldn't fine anything.

I have a 99 cherokee sport with 98k miles, 231 xcase, and 8.25 rear differentials. I am getting a thump, what seems like right under my seat whenever i tap the gas pedal or release the gas pedal.

It will do it whether i am going 5mph or 60mph. I could be accelerating, release the gas pedal = thump, then i press on the gas pedal again = thump. This noise underneath my seat is driving me crazy.

The front and rear u-joints are tight. So, I don't know if its my driveshaft making the noise whenever my engine is engaged.

Pretty much, whenever the engine is engaged and some torque is applied to the transmission, i get a thunk/thump. Its loud enough for me to notice and feel.

Anyone with a similar situation??? Thanks!
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  #2  
Old June 3rd, 2007, 17:16
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Re: Tap gas pedal = thump / clunk

Motor mounts or transmission mounts.
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  #3  
Old June 3rd, 2007, 17:54
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GrimmJeeper GrimmJeeper is offline
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Re: Tap gas pedal = thump / clunk

Quote:
Originally Posted by old_man
Motor mounts or transmission mounts.
yep. mine did the same thing, if it clunks when you let off the gas its the trans mount, but the XJ motor mounts are notorious for crapping out too.
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  #4  
Old June 3rd, 2007, 17:55
thenav thenav is offline
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Re: Tap gas pedal = thump / clunk

have the exact same problem, just that mines an 88.. let me know if you end up replaceing the motor mounts, if that corrects the problem. I myself will be replacing the t-mount.

Nav
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  #5  
Old June 3rd, 2007, 18:05
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Re: Tap gas pedal = thump / clunk

I'll have to check, my 96 makes the same noises and the drive components are all tight. Hope that this fixes it.
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  #6  
Old June 3rd, 2007, 19:48
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UNCC_99XJ UNCC_99XJ is offline
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Re: Tap gas pedal = thump / clunk

Mine does the same thing....same year and just about same miles as you too (i'm comin up on 96K probably tomorrow). I've found that slowly applying or releasing the skinny pedal makes a big difference in it.

I dont think its the motor mounts, but the tranny mounts are certainly a possibility.
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  #7  
Old June 3rd, 2007, 20:21
macrat123 macrat123 is offline
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Re: Tap gas pedal = thump / clunk

hmmm... I did have my tranny mounts replaced. However, it was done at Midas. Stupid i know, but i learned from it and tried to do my own work after that.

I'll try to see if the bolts are all correctly torqued. I was thinking about buying brown dog motor mounts. But before i do this, anyone with a similar problem fix it??
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  #8  
Old June 5th, 2007, 20:24
Todd XJ Todd XJ is offline
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Re: Tap gas pedal = thump / clunk

I have the same problem with my 01 with a 5 speed. I never minded it much but it's gotten worse. After going with the MORE motor mounts and replacing the tranny mount, I didn't notice it getting better.

I think it's more likely that it's slop in the rear driveshaft. Search for "driveline clunk" and you'll get a decent number of hits. Some people say greasing the transfer case output shaft fixes it, but going with an SYE is probably the better option.

I think I just decided that I'm going to install the AA SYE sooner rather than putting it off any longer. I'll let you know if that fixes the problem if you can hold off for a couple weeks.
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  #9  
Old June 5th, 2007, 21:35
macrat123 macrat123 is offline
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Re: Tap gas pedal = thump / clunk

I put some grease in the slip yoke but that didn't fix it. Greasing the slip yoke fixes a thump when you accelerate from a stop i think.

This is related to a thump while you hit the gas pedal while you are allready moving. I checked out my motor mounts tonight and it difinitely has play. So i am replacing it with brown dog motor mounts.

Either way, please let us know if that fixed your problem. it didn't fix it for me.
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  #10  
Old June 5th, 2007, 21:54
SimpleXJ SimpleXJ is offline
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Re: Tap gas pedal = thump / clunk

Have a friend help you diagnose it. Have them power brake the jeep in reverse and drive while you look for the problem.

SimpleXJ
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  #11  
Old June 27th, 2007, 19:26
macrat123 macrat123 is offline
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Re: Tap gas pedal = thump / clunk

I have replaced my motor mounts. Although it was cracked, it did not fix the clunk/thump problem while pressing the gas pedal and releasing the gas pedal while driving.

I greased the slip yoke, so that didn't fix it either. I'm really stump on this. Any of the previous posters fix the problem?

ToddXJ? did you fix it by putting SYE in?
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  #12  
Old June 27th, 2007, 20:16
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Re: Tap gas pedal = thump / clunk

Mine does this too, it's annoying as hell... If an SYE is the fix I'll get one...
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  #13  
Old January 6th, 2010, 21:36
floppy floppy is offline
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Re: Tap gas pedal = thump / clunk

Its not the SYE i have one and still have the problem. If you put it in Nuetral and rev the engine that would tell you if its motor mounts right?
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  #14  
Old January 6th, 2010, 21:43
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Re: Tap gas pedal = thump / clunk

had a similar situation on my 01 at about 80K. when replaced the clutch i had them put in a new tranny mount, cured it. gravediggin btw^
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  #15  
Old January 7th, 2010, 05:11
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Re: Tap gas pedal = thump / clunk

Check how much clearance you have below the exhaust pipe above the trans/t-case crossmember. When these Jeeps were new they had that problem from the factory. If the mount is good, see if you can loosen the exhaust at the manifold and push the pipe up to gain clearance . Then retighten the manifold flange bolts. I have also heated the pipe forward of the mount and pushed the exhaust up to gain clearance.
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