what could possibly be making a knocking sound under the floor of the passenger front footwell- sounds like someone hitting a dumpster with a hammer, hollow thunk. I’m running a crappy anchor tranny mount I’m switching to an OEM transmission mount. I have replaced the front upper and lower control arms and they’re torqued down. Anything else I should look at that’s causing the noise? It only happens on pretty big bumps and it’s only the passenger side.

 

I would check for exhaust clearance as it goes over the cross member. Also, look under the hood for something coming loose. Battery, etc. Shock bushing out will make a pretty good racket. Last thing I can think of would be ball joints on that side.

 

Is it actually knocking against the floor? Like can you feel it? or is it just coming from that area?

 

the girlfriend says she hears it, doesn’t feel it- but definitely coming from that area

 

Check out everything Supermn mentioned. Plus I would check the sway bar and pretty much everything suspension related. maybe you can get someone to rock the jeep back and forth or up and down really hard to create the noise

 

If it is really isolated to the front passenger foot well, I'm going to go with the passenger side upper or lower control arm. Is it possible they were over torqued and they are not rotating smoothly as they should? Were they torqued to spec? or just tightened down as much as possible?

Loose passenger side shock mount (upper or lower) and missing bump stop would be me runner up guesses.

Cross member and transmission mounts tend to be in the foot area of the rear passenger area.

 

your answer might be in this guys question.


https://www.cherokeeforum.com/f2/hel...estion-241039/

 

I will say I that torquing down the swaybar links does cure the issue but it comes back... a little backstory, my jeeps front coil buckets were rusted out so I had them replaced with arctec buckets. Doing so moved the axle side mounting bolt 2” higher than the stock location. So with a lifted OME kit I’m running moog OEM length swaybar links and they’re at a perfect angle- I just keep having to go back and retighten the top nut on the link.

Maybe be I’ll look into replacing the control arm bolts as well

 

new upper and lower control arm bolts, only one ill need to hit Fastenal up for is the UCA axle to arm bolt. the others I was able to find online- hopefully theyre here before the weekend. im still wondering if a shorter/crappy tranny mount could be the issue. either way ill have both replaced at the same time- all OEM parts.

 

So replaced the tranny mount with an OEM and boy what a difference. However the noise is still there- resembles someone hitting a dumpster with a hammer, an empty thunk. I had the shop replace the lower control arm bolts as well as the upper control arm bolts on the axle side- the body side are discontinued. Also had them retorque the trackbar. Nothing solves the issue, I tightened the shock and tightened the top bolt on the swaybar links and still- THUNK! Any suggestions? It almost seems like somethings binding up.

 

How are the sway bar frame bushings? Could the bar be loose and banging against the frame?

 

 

If you're absolutely certain that it's not a loose exhaust pipe or movement in the tranny or engine mounts then I might try jacking up the front end so the tires are off the ground (with a good solid block behind the rear tires on each side), putting a jack stand under the driver's side axle as far to the outside as possible, then putting a jack stand under the passenger side and very slowly using a floor jack with a flat piece of wood on top to push the passenger tire upward. I'd use a trusted assistant to operate the jack while I watched the suspension components as the passenger side compresses. If nothing jumps out as the culprit then I'd jack up both sides so you have a good 4-6 inches under the tires and then use the jack to slowly lower the passenger side and again watch the suspension as the passenger side extends.
In other words, simulate the effect of hitting a large bump where you can watch how everything moves.

The classic culprit of knocking as described is an issue with the shock or spring, but it's hard to know since there are so many moving parts in that area of the vehicle.