Help me diagnose a noise

ShimShim

ShimShim

Well-Known Member
Joined
Apr 21, 2005
Location
Charlotte, NC
2001 TJ 4.0L with Auto Trans.
When I shift from reverse to drive, or even when I step on the gas hard from a complete stop, I hear a loud click/clunk from underneath. I can't tell if it's coming from the rear diff or from the transfer case. I don't know if I have loose gears or what. Nothing has been worked on/changed for quite some time. It started a few weeks ago and seems like it may be getting worse. Any ideas?

Thanks for any help.

Brian
 
In neutral with wheels blocked to keep it from moving. Get under it and move the drive shaft to check u-joints. Check links for wore bushings and or breaks. Check play in rear diff. Check all links and suspension parts.
 
I'm a newb but I'll chime in anyway. I don't think it's the transfer case or the diff. They are tightly set and I wouldn't expect lound clunks from them under those circumstances. I'd be more likely to expect regular clicks.

I like the u-joint idea from upnover. It's a crazy thought but I wonder if loose ubolts would allow the housing to rotate a little under torque and make a loud clunk.

If it was me I'd get a buddy and hang from the side of the truck while driving in a parking lot (slowly) to help identify the location of the sound. 60 second of standing on a rock slider can save 30 minutes of random looking around.
 
check the cross member bolts and make sure they are tight.

else, whn load applied rotational forces may cause cross member to slap against frame
 
Noise problem

Mine does the same but I have a manual trans. If you dont have a SYE, it is probably the drive shaft binding up when you punch the gas and it goes from still to rotating fast. Mine does the same when I go up hills or punch the gas at take offs. I can also feel a knocking noise on the floor when it makes the noise, just wondering if yours is doing the same. The noise won't go away until you install a SYE, which I plan to do on mine asap to fix my clunk noise. Hope this helps.
 
vanguard said:
It's a crazy thought but I wonder if loose ubolts would allow the housing to rotate a little under torque and make a loud clunk.
Click to expand...

No u-bolts on a TJ. I'm betting u-joint or u-joint straps.
 
OK, I tried Chip's suggestion. There is about 1/8 to 1/4 inch of play in the transfer case when I try to turn the D/S, don't know if that's a lot or not.
The U-joints and straps seem to be in good shape.
I checked the crossmember, it's stable and bolts are tight.
I also checked the control arms, they don't seem to be loose.
Springs don't budge.
A little info I didn't pass on, but probably important....
I have a 4" skyjacker lift with 33" tires, and Yes, I do have an SYE.
I haven't had the chance to hang upside down and watch while my friend drives....but I'll do that as soon as I get a couple of :beer: :beer: .
Any other suggestions? Keep em coming.
Thanks
 
Just pop off the rear driveshaft and take off the ujoint caps. Check to see the condition of the needlebearings. More than likely that will be the cause of the clunking and it doesnt take but a couple minutes to check, cause you dont want that d-shaft falling out going down the road. Goodluck on the project.

Leach
 
Check tranny mount, do this by jacking tanny up to see if it separates from mount.
Do you try twisting, and pushing up and down on the drive shaft?
Also, some times hard to see movement, I use a long Screw driver for a little leverage to try and make it move.
Could also be a engine mount, check it the same way as the tranny mount.
Hope this helps
 
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