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Weird Driveline "Clunk" - Ideas?

PurpleBeeper

PurpleBeeper

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70 Roadrunner 4spd car --> I've had a weird sound in my car after I shut it off. Everything seems normal once it's parked & turned off, then "clunk"...…………………"clunk"...……………."clunk". It seems like it's under the car somewhere & sounds like a metal-on-metal sound which repeats about 4-5 times roughly 1 minute apart.

I "thought" it might have been something binding in my leaf springs & the suspension was just unloading. However, yesterday I fired it up & didn't even put the car in gear. I did let the clutch out after the engine warmed up a little, but I never put the car in gear or moved it.

Any ideas at all?

YOUR HELP IS APPRECIATED! THANK YOU!
 
PurpleBeeper said:
70 Roadrunner 4spd car --> I've had a weird sound in my car after I shut it off. Everything seems normal once it's parked & turned off, then "clunk"...…………………"clunk"...……………."clunk". It seems like it's under the car somewhere & sounds like a metal-on-metal sound which repeats about 4-5 times roughly 1 minute apart.

I "thought" it might have been something binding in my leaf springs & the suspension was just unloading. However, yesterday I fired it up & didn't even put the car in gear. I did let the clutch out after the engine warmed up a little, but I never put the car in gear or moved it.

Any ideas at all?

YOUR HELP IS APPRECIATED! THANK YOU!
Click to expand...
wait,when its turned off?its making clunk noise after how long of driving?,try looking under her,maybe get a friend to help listen where sound is coming from.
 
I say exhaust pipe touching something, a bracket loose, letting it move slightly as it cools
 
Thanks guys... I know this is like the 3-Stooges with Curly looking for a "squeak"... Hey Moe, what's a squeak look like?
1. Yes, it makes the "clunk"(s) AFTER the engine is turned off...& after not driving it AT ALL, just running the engine for 5-10min.
2. Definitely not dieseling
3. Exhaust....hmmmm….maybe, hadn't thought of that.

It sounds pretty "solid metal-on-metal", sort of like someone has a small hammer and hits the middle of the driveshaft. I'd thought about maybe something in the clutch binding/slipping OR maybe something just not right in the rear end, except yesterday the car never moved an inch. I wish I could take a video with sound :(
 
PurpleBeeper said:
Thanks guys... I know this is like the 3-Stooges with Curly looking for a "squeak"... Hey Moe, what's a squeak look like?
1. Yes, it makes the "clunk"(s) AFTER the engine is turned off...& after not driving it AT ALL, just running the engine for 5-10min.
2. Definitely not dieseling
3. Exhaust....hmmmm….maybe, hadn't thought of that.

It sounds pretty "solid metal-on-metal", sort of like someone has a small hammer and hits the middle of the driveshaft. I'd thought about maybe something in the clutch binding/slipping OR maybe something just not right in the rear end, except yesterday the car never moved an inch. I wish I could take a video with sound :(
Click to expand...
well move your a..,,get the vid on your phone ,get it on you tube,,,ggetttr done.‍♂️‍♂️‍♂️
 
I'm betting it's exhaust related. We had a loud rattle on our Grand Cherokee recently. I could tell it was coming from underneath toward the back. It was off and on while driving and especially while stopped at a light. I was pretty sure and later able to confirm it to be exhaust related after I got it over a service pit and had a look. It was a loose exhaust clamp allowing the tailpipe to rotate, which made it come in contact with a metal gusset near the spare tire. I rotated it back and tightened the clamp and that was that. I know yours is happening after it's shut off, but I'm still thinking exhaust. Our Jeep will make noises like you describe in the garage after it's shut off. As I said earlier, I think it's metal contracting while cooling - probably in the exhaust on our Jeep.
 
My bet is heat related (exhaust as everyone has suggested) comes to mind as most likely. I would wonder about a joint in the exhaust system or muffler, or the case itself expanding and then contracting

Won't a video just be looking at a nonrunning car with a clunk every minute or so. One piece of advice. If you shoot a video, don't hold the phone vertically.

Why not heat it up, put down a mat in the middle of the car and lie down with your head under the car waiting. That will tell you if it is front or back and may let you localize it further. You could also break out a sixpack, invited some friends over to help and cover more of the car.
 
Thanks for all of your suggestions. My phone broke and I don't have the money right now to replace it & I'm using a 15yr. old flip phone (no video capability)...sorry. I also don't have access to a hoist, but I do have a piece of cardboard I could lay down on and see if I can better identify where the sound is coming from. It sure does "sound" like it's coming from the driveshaft somewhere, but the exhaust idea is very possible.

I just ran a test a few minutes ago. I started the engine (dead cold) and ran it for 3-4 minutes, keeping my foot on the clutch pedal the whole time, then shut it off. I heard one "clunk" about 1 min. later. To me, this indicates it's not actually anything in the driveline (?) since the nothing in the driveline ever moved. (fyi- this sound isn't heard while driving the car, only after shutting it off)

I'm going to see if I can lay down next to the car & see if I can narrow it down. I also haven't heard the sound after just sitting in the car (not starting it), so I think that rules out my "butt weight" loading/unloading the leaf springs. Exhaust "something" seems like the odds-on favorite.
 
Check engine and trans mounts.
 
5.7 hemi said:
Check engine and trans mounts.
Click to expand...
Maybe. I just put a new urethane trans mount in 6 months ago & the engine mounts are solid....but that doesn't mean I don't have a loose bolt. I will check that too.
 
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