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It's NOT the flexplate...what is causing this sound?!

C

citRon

NAXJA Forum User
Location
loohaville kentuck
So, the last 2 weeks (1-2 hours at a time) have been spent in the garage on the floor taking the tranny out to get to the flexplate...which I was convinced was cracked. I've had that 'rocks in a can' sound you get when the flexplate bolts are loose, or the plate itself is cracked. No cracks. I even pried on it, no warping, no looseness. Previously I had removed the oilpan, and checked the bottom bearings to rule that out. Everything looked good, replaced the oil pump and rear main while I was in there.
So...Flexplate is ok...bearings looked ok....What else can this be? The noise is loud, I'm waiting for the thing to explode! Well, if I ever get the tranny and engine mated back together that is.
 
Or it could just be the notorious piston slap.

Every Jeep I've owned or ridden in pre '96 had it at idle up to about 1300 rpms.

I just live with it now lol.
 
Did you just check the main bearings or did you check the rod bearings too?
 
My tcase chain would make a hell of a rattling noise, but only while moving down the road, and only with it in 4x4.

It was low on tcase fluid and the chain was streched big time.

Now it is as quite as when I bought it new, well the mudders make a little noise. ;)
 
Did you remove the plate when you looked at it?
not being a smart ass, but the cracks are fricking tiny!
Mine had none anywhere obvious around the outside, but from bolt to bolt. They felt like crud buildup to the finger. The noise would go away at first under load. When I layed it on a surface and tapped around the bolt pattern, it would rattle. And off the vehicle, they were much more obvious.
Sincerely, hope you don't have to tear it all down again.
 
Check to make sure the harmonic balancer is not rubbing the timming chain cover. The outer rings will slip off the rubber and almost always slide back into the cover. It will rub a hole in the timming chain cover if let continued to run like this.
 
Have you poked around with a sounding device like a piece of broom handle or a stethoscope? It will narrow down the search.

citRon said:
So, the last 2 weeks (1-2 hours at a time) have been spent in the garage on the floor taking the tranny out to get to the flexplate...which I was convinced was cracked. I've had that 'rocks in a can' sound you get when the flexplate bolts are loose, or the plate itself is cracked. No cracks. I even pried on it, no warping, no looseness. Previously I had removed the oilpan, and checked the bottom bearings to rule that out. Everything looked good, replaced the oil pump and rear main while I was in there.
So...Flexplate is ok...bearings looked ok....What else can this be? The noise is loud, I'm waiting for the thing to explode! Well, if I ever get the tranny and engine mated back together that is.
Click to expand...
 
My XJ's torque converter went twice. The first time because I ran synthetic fluid through it. The second one went because the bolts that hold the transmission to the block came loose and the transmission pulled away from the block. Shortly thereafter the TC started making noise again. It's embarassingly noisey but the vehicle runs fine.

Unfortuantely, I was broadsided yesterday and rolled my XJ. At least now I don't need to drop the transmission and replace the TC again! Good luck Ron.

Rich
 
Since you pulled your oil pan I'd assume you thought the noise was comming from the bottom end of your motor. If your main bearings are fine it sounds like the piston rod bearings are shot.
 
I had a noise like that, I had just installed a new clutch and an inertia ring on the flywheel so I was super worried. Ended up just being the exhaust pipe rattling on my crossmember, it would only do it when I gave it gas and the engine torqued to the side a little. Much relief that was...
 
I'll have to follow this thread for all the ideas and possibilities. My 89 has had this rattle for years and I haven't been able to track down the source. I always thought it is the converter bolts until I took the inspection plate off 2 weeks ago and all the bolts were tight and there was no evidence of cracks. Back to square one.

In my case, the rattling noise goes away when the Jeep is all warmed up. Until then, oh my.

I am thinking the transfer case chain is stretched, but would the rattle go away when it's all warmed up? I would think it would get worse. I don't know.

Good luck finding the source and post back when you do.
 
Allright guys, thank you so much for the replies! I've been away, working 18 hour days, so no time to check back here.

Ok, the noise: definitely coming from the bottom/rear of the engine- checked with a stethoscope, coming from bellhousing or crank area as listening to with it touching the oil pan and bellhousing. Oil pressure is good and steady all the time. Not the cat or exhaust or t-case. Tranny fluid was kept checked, always full. When I drained it, it was dirty, dark brown.
I didn't take the flexplate out, because I looked at it really close, pryed on it, and couldn't see any movement whatsoever.
When I had the oil pan off, I checked the main bearings only.
I don't think it is common piston slap since it comes from the bottom rear, and I've had other 4 liters with that and it is a different sound.
Sound comes on quickly after start up, doesn't go away through the rpm's. If it increases in speed, it is very very slight. It sounds exactly like you put a bolt in a can and started tumbling it fast.
 
STILL chasing this noise!
Today I took it to a friend who happens to be a Jeep mechanic- worked a t a jeep dealership 20+ years. He said it's coming from the bellhousing (like I thought) and maybe it's the Torque Converter since i didn't see any cracks on the flexplate.
He said just drive it- it's not going to hurt anything, and see if it gets louder or worse. He said it's definitely nothing wrong with the engine.
He said there was no way to tell if the TC was bad unless you replace it.

Anyone have anything else to add? I'm wanting to sell this thing, but that's not going to go well with a rattle!
 
I get the same noise with mine and I know it's the torque converter and plan to drive it till it goes out then replace it..I like you checked my flex plate and what not..I also had to replace my motor so mine has a new motor and I know everything is tight and every trany shop that has listened to it says the same thing torque converter and drive it till it goes out then replace it with a factory converter as after markets will not last.. Just my 2 cents worth..
 
great- thanks! Always good to get a 2nd opinion. I was wondering about just getting a used TC from the pull-a-part for $20 bucks and having them swapped out. I tried to find one online and came up empty. I need to sell this thing, and the 'rocks in a can' sound probably won't help sell it, even if you tell people what it is! It only has 93,000 miles on it.
 
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