1984 CJ7 underchassis banging/crackingscratching sounds

[danielle]

Hi! guys, my friend owns a 1984 jeep, he made some paint work and design and it was quite impressive. But then when we rode the jeep for a test drive every time we encounter a hump on the road we hear this terrible sound... I could not even imagine how to describe the sound but it seems like its a cracking sound and its as if there is something that is going to be rip off. When we checked it out it seems everything was fine. could you help my friend with this?

 

[CJ]

Hello danielle and welcome to our site!

When you say you checked everything - can you list the items?

It sure sounds like a suspension component is loose or some thing is rubbing. Can you see and fresh marks where something may be moving and scraping on another piece?

 

[Old Dog]

I would start by checking the spring and shackel mounts, as they can break where they mount to the frame.

 

[elwood blues]

It could also be the exhaust system too. If something has broken loose, and it's banging around, ask me how I know this one...


BTW

 

[gert]

I could tell you some good stories envolving coat hangers If you hear some bad sounds then something is not right It would be a real good idea to find out what it is before you drive it again.

 

[danielle]

Thanks for your warm welcome. well our initial reaction about the uncomfortable sound is to look underneath the jeep. My friend checked the spring mountings or shock absorbers but according to him it seems alright. He is quite hesitant to bring it to a mechanic because currently he has Limited funds because of the painting job, he had to spend a quite significant amount. Besides the spring mounts, exhaust system and coat hangers what else should he check? I'm gonna call him later about your help maybe he could save a few bucks... thank a lot guys

 

[kicknjeep]

I would have to agree with the shackle mount to the frame, sometimes you can look and even grab and try to move them and still not see anywhere they have may have a weld that has separated (Don't ask). if they are ok then check the bushings. is there much if any rust in the frame?.

 

[Old Dog]

I check my spring hangers and shackel mounts by jacking the tires off the ground, and putting jackstands under the frame, than the supension hangs free and will seperate if broken.
As kicknjeep said just sitting with the tires on the ground it's hard to tell.
Let us know what you guys find it's hard to tell about strange noises.

 

[Cweed]

Check the pinion angle on the rear axle. This will sometimes sound like a popping, grinding or banging noise. If it is on the edge going over a hump can create binding in the U-joint. You may simple need a degree shim to correct.

 

[kicknjeep]

just a thought, I had an 79 CJ5 that when the rear end was about to give up the ghost it made a sound similar to this also and found out almost no fluid in the rear end. Ok i was a little younger and a lot dumber but couldn't hurt to check it out...

 

[coldwater]

OK, off topic, but there was a PITA arse kid in the neighborhood a few years ago that got his license, bought $100 POS S10 pick up, cobbled on one of those garbage can mufflers, and would fly by my house in the middle of the night waking me up. I saw his car in a lot one day, and took it upon myself to put an 18" heavy duty tie wrap around the driveshaft. That evening, I saw a AAA towing his POS up to his house, and I never saw the truck again. Guess he never figured it out.

stupid punk.

Moral of the story, you never know where driveline noises will come from!

 

[danielle]

Just called my friends who owns a CJ that creates a weird ripping sound whenever we slowdown to approach and pass a hump. I told him about your suggestions and he want me to ask you guys is it possible that the sound came from a loose engine support because the other day he was warming up the engine just to keep the batteries from dying because he was not able to use the jeep since the undiagnosed jeep sound occurred. When he applied gas while the gear is in neutral, according to him the sound reoccured even the jeep was on full stop. How i wish i could explain it to you better but i was not there. He suspects that every time the engine vibrates the jeep will create that ripping sound because of the loose engine support. what do you think?

 

[CJ]

It could easily be a broken engine or Transmission mount. Anything that is part of the undercarriage, drive line or suspension. The engine could be torquing over as you let of or on the throttle causing a drive line binding.

 

[Cweed]

One other possibilty is a broken baffle in the muffler. I had this happen once on a chevy pick up and it started off as a slight rattle and grew to a bang until it broke off and plugged the exhaust. Boy things you learn as a kid.

 

[BrockGrimes]

An easy way to see if it's a mount is, start it up, put it in gear, hold the brake down hard, and give it a little gas, if the engine moves quite a bit it's a mount, if it doesn't put it in reverse and try it again, if it still doesn't move, then it's not a mount.

Also check the Transmission mount, and any support mounts.
My '79 CJ5 has 2 support mounts next to the Transmission and made a good racket when they wore out. Also check the center cross member the Transmission /Transfer Case is bolted to.