Noise under floorboard

[joeylead]

Ok so I have been trying to fix this issue for a long time. I have a 97 tj, 4.0, 5 spd. 4" lift and 35" tires. I am getting a kind of thumping sound under me feet when I take off, or when the drivetrain is under a hard load. I have read other posts and it is usually attributed to the drivetrain shifting under load. So what i have done is: replaced the shift rod linkage bushing and rubber parts, they were totally wasted, replaced the transmission mount, it was half off the metal backing plate, and lastly replaced the engine mounts, the drivers side seemed ok, but the passenger side was a little soft.


At this point, the noise is still there and no better. At least the parts i am replacing neede it...lol. Anyone have a suggestion as to where I should look next? And advice would be appreciated. Thanks.

 

[greg92jeepxj]

The exhaust is the only other item that comes to mind , are any mounts looses , bent or otherwise ? My exhaust is tight , but the tailpipe is too close to the fuel tank and rattles ( thanks to Rockauto and FedEx) because its probably a little bent. Check if any pipe is too close to the floor since it runs under the drivers side. But yes , it's good you changed the other parts , hard work but a bummer when the problem still exists.

 

[joeylead]

oh right the exhaust is a likely potential cause, i ll check tomorrow. its funny how things go, yes in theory, i didnt need to absolutely change the engine mounts, but my brake lines are ally reuted and crusty and needed to be replaced and while ding the drivers side mount i jarred the lines hard enough to cause one to leak rea bad. so this will motivate me tonow replace all the lines. just need time...lol

 

[8177]

I usually don't thread jack someone's post when they are asking for help but I swear this is a true story. When I was in the navy working on A-7E corsairs A pilot came back and wrote a discrepancy about a noise coming from under his feet that sounded like a little man with a hammer. The technician found a broken shock mount on a piece of gear but signed the gripe off as. "Took Hammer away from tiny man". I apologize joeylead. But I couldn't help it. I was waiting for you to say it sounds like someone hammering on the floorboards but you didn't.

 

[Bounty__Hunter]

Have you checked the transfer case fluid? It's possible that a stretched transfer case chain could be banging around inside the case.

 

[JPNinPA]

Check u- joints and axel u-joints. Also check sway bar end links.

 

[joeylead]

Thanks for the advice guys. ANd truth be told, it does sound like someone tapping under there with a little hamer...lol. the jeep is sidelined with the broken brake line (long story). but while it has been sitting i have checked a few things. the swaybar endlinks look fine, but ill order new quick disconnects anyway, good excuse to get them. the exhaust is clear of the body. shock buchings are ok. i am concerned about the tcase. besides the fluid, how else can i tell if it is going bad? it is right in the area of the noise. also, how do i check to see if the upper control arm mount bushings are bad?

 

[Bounty__Hunter]

Change the fluid in the t-case and check it for aluminum shavings, this would indicate a stretched chain hitting the inside of the case. Check the magnetic drain plug. Fluid should be a bright clear red.

 

[jfrabat]

If the sound frequency depends on speed, check your ring and pinions. Mine went out a couple of weeks ago, and there was an intermittent sound coming from under the Jeep (a kind of thump-thump, thump-thump that seem to come from the transmission area even though it was the rear diff).

 

[joeylead]

Ok i think i found the noise, i have tubular lower control arms that came with te jeep. well the frame end bushings are totally shot. put a prybar and there was a ton of movement. not to try to figure out what arms they are and if i can replace the bushings or just get new arms.

 

[JPNinPA]

Ok i think i found the noise, i have tubular lower control arms that came with te jeep. well the frame end bushings are totally shot. put a prybar and there was a ton of movement. not to try to figure out what arms they are and if i can replace the bushings or just get new arms.

Post a pic of the bar.