Hellish Pop Noise Causing thunk in Floor Pan (Will scare you when it happens!)

When I pull over on the right hand shoulder of the road and back up with the wheel turned to the extreme left and back up (as if to back up in the road and turn around) I have a horribly loud single pop sound that rattles the floor and seat of my XJ (the pop will occur if I pull over on the left hand side of the road and turn the wheel to the extreme right and back up). I have pulled the front drive shaft and replaced the bearings in the rear end. The problem still exists. I do have 187,000 miles. I did have a broken motor mount but am unsure if this is a sign of the problem. It feels as if the tension builds and is suddenly released with a huge pop. I pulled the pan on the transmission and found no metal. I did not have excessive wear in the rear end. I believe it is to loud to be a ujoint on the front end axles. I can't find any problems. I have pulled the transfer case apart and replaced my chain and sprockets. There is no wear visible in the transfer case at present with 10,000 miles on the chain and sprockets. Please respond with pictures of what to check or modifications that need to be made. I do not have a lift kit and have a 242 transfer case.

I'd look at the trac bar and it's mout nupfront
THe steering linkages and rod ends
LCA and UCA bushings
In that order. Make sure they're all tight with no slop.
Rubber bushings that are cracked or show signs of wear should be replaced.

also just check Ujoints to rule them out as a culprit for anything (its always good to check them for slop)

Does this sound remotely familiar to anyone? I have felt a slight grab when taking curves at highway speeds. I'm not sure if this is related. I do see slight cupping on the tires.

I'm trying to brainstorm, because I am so lost.

I'm an experienced do it yourselfer but this is very unusual.

Does this sound remotely familiar to anyone? I have felt a slight grab when taking curves at highway speeds. I'm not sure if this is related. I do see slight cupping on the tires.

I'm trying to brainstorm, because I am so lost.

I'm an experienced do it yourselfer but this is very unusual.

Check the bushings in the Upper and lower controll arms.
# 31, 32, 33, & 34 in the attached diagram.
http://www.quadratec.com/advisor/jeep_oem_replacement_parts/suspension/Cherokee_XJ_suspension.php

They are o.k., what should I check next!:skull1:

I have the same problem with no clear answer, I hope you can find one

Accelerator position doesn't seem to matter much in the process. I can back up out of my driveway and put the truck in gear and will get the same teeth gritting experience. Anyone having this symptom?

You lost me....Do you mean when backing up straight out of your driveway it does it too, or only when you turn the wheel like your first post? Accelerator position ? Do you mean it doesn't matter how fast you are going, or what?
Does it do it in both 2 and 4 wheel drive? Loads are different on different parts in 2 or 4 wheel drive; that may give you a clue. #1 check for me would be the front axle u joints though....

Year, engine sz, tranny and xfer case type might also be useful for others to help u

1998 Cherokee Limited 4.0 242 8.25 w/ 3.55s
Acceleration doesn't matter - velocity doesn't contribute to the intesity of the pop
2x and 4x give the same result a pop
I'll replace the u-joints but I'm not getting slop out of them when prying on them with a screw driver

The fact that I get a jarring of the floor pan should help us identify the problem, but I can't figure it out!

The rear end appears to be ok, but why would I get a jarring in the pan? The transmission is bolted to the crossmember and could just slap the body (there are no signs of contact between the transmission and body and transfer case)

Where else to look?

The pop occurs after the wheel has been turned in motion and the vehicle is stopped and then travels in the opposite direction approximately 5 ft.

Anyone have any new suggestions?

Thanks,

The fact that I get a jarring of the floor pan should help us identify the problem, but I can't figure it out!

moparhorizon said:

I did have a broken motor mount but am unsure if this is a sign of the problem.

Click to expand...

If you have a broken motor mount and something is smacking your floor pan it is hard to believe they are not related.

when i was much younger and stupider i had a valiant i shoehorned a 440 into. not surprisingingly i broke motor mounts regularly. i could tell i broke one when i got on the skinny pedal and the steering locked. the torque would let it rock enough for the exhaust manifold that i ground for clearance to grab the shaft. like a said younger and STUPIDER.

moparhorizon said:

Anyone have any new suggestions?

Thanks,

The fact that I get a jarring of the floor pan should help us identify the problem, but I can't figure it out!

Click to expand...

the unit body can make sounds travel in unusual ways.
I swore that I had a nasty noise from the front, until I got out and had someone else drive it past me. It was a rear drum.

Sounds like a stumper, maybe the barpins, loose shock??? Wheel bearings, transmission mount, motor mount, just brainstorming here. Possibly loose hub??? I really am not sure unless I am next to the XJ, but hope that helped with some ideas. JOE>

Maybe it's the steering stabilizer binding.....? I think a clue is that the pop occurs when the steering is turned to full lock. You might try disconnecting it on one end and then testing for the pop.

If you still have the stock slip yoke set up, I'd venture to say the slip yoke is binding on the tailshaft as you go from forward to reverse; resulting in the pop you describe in the area of your rig.

The fix is to remove the rear driveshaft, and lube up the splines and the slip yoke with copious amounts of grease to alleviate the binding....