My friend and I swapped C4's in his mustang. A neighbor gave him one that was supposedly rebuilt and since the one he had was shifting a little too hard and had tons of delay shifting into gear we figured what they hey we'll try the other one.

We swapped it in and it has a constant and rhythmic knocking sound comming from it. A metal on metal sound. We know it is not an exhaust leak and is not coming from the engine, definately from the tranny. I've double and triple checked to make sure all of the torque convert nuts are tight, the starter isn't getting snagged the bell housing is on properly. I have also eliminated the possibilty that the car is not properly shifting into gears (linkage adjustment) if this is the case it would be from inside the tranny not out. I have also made sure there isn't anyhting on the outside vibrating (linkage, line etc) but like i said the sound was rhythmic and speeds up/slows down with engine rpms. We have ran the car through the gears a few times to make sure the fuild is properly filled and that the torque converter is also full.

This knocking sound occurs in all gears including neutral and park. Since it does happen in park my thought is it may have something to do with either the torque converter or the tranny pump. But, I know for fact the converter worked fine when we took it out and it was set aside and covered up so it definately doesn't have anything in it, nor has anything happened to it.

Any thoughts?

Scott

 

the torque converter bolts might not be lined up with the coressponding holes in the flywheel... thats my thought

 

If i'm correct in when it comes to the fly wheel there are a set of smaller holes (for the studs) a i can't remember if there is one or two larger holes for the drain plug. And we lined the studs up on the smaller set of holes.

 

I'm pretty sure that there is a specific pattern to the bolt holes so that it has to be aligned properly with the torque converter to be installed.

 

When bolting the flywheel to the engine, yes there is a specific bolt patter and we got it to line up. Does anyone know if its possible to bolt it up incorrectly...as in arranging the bolt in a certain order will be close enough to mount , but not right.

If you refering to torque converter to flywheel I thought the four smaller holes were on an equal/generic pattern.

 

Scott
Jack it up and secure it. and crawl under while running and in gear and get a long screw driver and hold it to your ear and to the trans, this will determine where the noise is coming from in the trans. After that it's easier to rule stuff out.
Be safe

 

It is possible to bolt it up incorrectly. Been there. But the weight on your flex plate will hit, I think it was the starter. It's been quite a few years since I did that. Pull the inspection plate/dust cover and using a ratchet, crank the engine around and see if there's wear on the weight. If there is, you'll have to realign. If that doesn't solve the problem, run the car and while it's still cold, use your hand and see if you can feel where the vibration is coming from. I recently had three bolts come loose from flexplate to crankshaft and it created a metallic rattling/clunking. It was horrible and I could feel it when I touched the oil pan where it meets the tranny.

 

GUYS THANKS!.. I had already used the old screw driver technique and was unable to determine whether the sound was coming from the tranny or the bellhousing area...at first it seemed like the flywheel was hitting something, ( i pulled the inspection plate off) but i wasn't seeing any metal shavings so i assumed something inside the tranny..Looks like we will pull her off and check the flywheel again. THANKS.

Anyone else have any ideas?

 

Oh, and it could also be a cracked flexplate.

I'm gonna go out on a limb here an post a link to a video I did when I had what turned out to be the loose bolts on the flexplate. I posted this video so some guys could listen and the ones who responded said it was most likely a cracked flexplate, loose flexplate or busted torque converter.

When I didn't know what was wrong, but it was loud and scary

Maybe it sounds like what yours does.

 

Mine's not quite that loud. but the exact same thing...see i watched the flexplate at about 500 rpms and it seemed (yeah hard to watch that lol) that i could see the counter balance right before it knocked, but i wasn't seeing any shavings. Hopefully i go home to find a flexplate thats been installed wrong.