Hey guys,

Just finished my 3rd trans fluid drain and fill. When I got the Jeep 2 months ago the fluid was brown and nasty, thankfully it's finally getting pink again.

Took it for a test drive, stopped at a stop sign and at idle, I hear a faint thud, thud, thud, thud...

It only does it at idle, its not a tick or tap but a pulsing thud like if you were to tap on the firewall with a rubber mallet. It's on the passenger side, you can only hear it from inside the cherokee near the passenger foot well.

I did feel around and you can feel pulses from around the thing I circled in the picture or from putting your hand on the firewall behind it. If you go to the drivers side you can't feel it at all on the firewall.

There is also a coffee can sized plastic can with vacuum lines coming out of it next to the thing circled in the pic . If you put your hands on the lines you can feel the pulse on them too.

Checked all of my connections etc, all look good. It may just be a coincidence that this showed up after the trans service but, i drove it yesterday and did not hear the noise.

Ideas? I don't even know where to start on this one.

 

Sorry but I have no idea what the noise could be. The thing you circled in the pic is the receiver/dryer in the air conditioning system. The black coffee can looking thing next to it should be the evap canister to to with the evaporative emissions system. Neither of which should be thumping.

 

yeah, that's what I figured. It may not be coming from either of those, the thud/pulse is coming from somewhere in that firewall area.

 

possibly you motor or trans mounts check and see if there are any signs of breaking and or cracking and replace accordingly

 

Where is the Evap. system solenoid located in that vehicle? They make noise when they cycle, and it's usually never diagnosed. On my WJ there was a recall or TSB where the dealer installed an isolator on the Evap. solenoid mount on the driver's inner fender to quiten the noise. On my ZJ I used faucet washers between the mount and the fender to achieve the same results. Redneck remedy.

 

Hmmm, interesting point on the evap mount. It's so hard to tell where it's coming from with the engine noise while running. I will have to start pushing up against stuff around that area to see if it makes a difference.