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Thump underneath on acceleration

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Old Oct 7, 2014 | 09:31 AM
  #1  
BrianShort1983's Avatar
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Default Thump underneath on acceleration

I'm new to the site but long time browser .. So here it goes I have been chasing a gremlin for some time now and i'm tired of throwing parts at it . On hard acceleration I get a repetitive thump on the floor board , and on right hand turn's under acceleration . Not just a one time thud but continuously . I can make it happen with no throttle coasting and start leaning the wheel to the right . History - New axle joint's , trac bar , upper and lower ball joint's , new lower control arm's . The front end is tight and drive's well until I turn right and accelerate it sounds like someone is pounding on the floor . It does absolutely nothing turning left . The mounts' all seem tight . Any help or idea's would be greatly appreciated . Thanks in advance
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Old Oct 7, 2014 | 09:52 AM
  #2  
jeeper jason's Avatar
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From: Western, Pa (5 mins away from ohio border)
Year: 1999
Model: Cherokee
Engine: straight 6 (4.0L)
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Can you get it on video (the sound)
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Old Oct 7, 2014 | 10:13 AM
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Replace your transmission mount.
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Old Oct 7, 2014 | 10:20 AM
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You can take a large pry bar and check it. But they are easy to replace and inexpensive.

I checked mine by hand. Thought it was fine. That same thumping noise continued. Finally got It on a lift and tool a large pry bar to it. It was completely broken in half! After the new mount was installed no more thumping.

Last edited by holycaveman; Oct 7, 2014 at 10:23 AM.
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Old Oct 7, 2014 | 10:29 AM
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From: Pittsburgh, PA
Year: 1998
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Originally Posted by holycaveman
You can take a large pry bar and check it. But they are easy to replace and inexpensive.

I checked mine by hand. Thought it was fine. That same thumping noise continued. Finally got It on a lift and tool a large pry bar to it. It was completely broken in half! After the new mount was installed no more thumping.
True that ^ I had a 98 5 speed cherokee that had a clunk everytime I let the clutch out, went through the front end and rear end with no luck. Finally I did the transmission mount and it was working in unison with the rear driveshaft and the thud I got was from the 4wd linkage working its way loose in the floor mount bracket
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Old Oct 7, 2014 | 12:24 PM
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Default thumping

As for the video I can not at this moment . I will check the trans mount again .I will report back as soon as I can . Thanks for the responses .
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Old Oct 7, 2014 | 07:17 PM
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aka"dude"'s Avatar
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From: north east CT
Year: 1998
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How much lift are you running? Have you done a SYE yet?
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Old Oct 7, 2014 | 07:52 PM
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My cat thumps the floor on acceleration
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Old Oct 8, 2014 | 08:30 AM
  #9  
cruiser54's Avatar
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From: Prescott, Az
Year: 1990
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Originally Posted by holycaveman
You can take a large pry bar and check it. But they are easy to replace and inexpensive.

I checked mine by hand. Thought it was fine. That same thumping noise continued. Finally got It on a lift and tool a large pry bar to it. It was completely broken in half! After the new mount was installed no more thumping.
This^^. Also look at the mounting bolts for the trans mount. Engine mounts being worn can also contribute to the issue. No videos needed, just some noggin pokin' on your end.
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Old Oct 8, 2014 | 08:36 AM
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Fred/N0AZZ's Avatar
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From: Monett, MO.
Year: 1999
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My engine and transmission mounts were both bad and I didn't even know it till I checked them one day when underneath checking the tailpipe.

IMHO if one of them is bad I would replace both unless you can see that the other is newer.
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Old Oct 8, 2014 | 08:38 AM
  #11  
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I bought it with only a 3" on it .... going 8 1/2 in spring !! .. Pulling it in tomorrow evening to bend and pry the hell out of it I will report back thanks for the help so far .
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Old Oct 8, 2014 | 08:43 AM
  #12  
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From: Albuquerque, NM
Year: 1999
Model: Cherokee
Engine: 4.0
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It might be the muffler hitting also. Mine used to before I replaced it and got all new hanger bushings
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