my LT1/T56 clutch sounds like a can of marbles

[WS6]

i thought maybe i had an odd problem but in doing some research i found someone else who mentioned having a similar sound, but they really didnt say what the problem was. so heres what is happening to me and everyone can give their best guesses.

the car drives and shifts perfectly fine but it sounds horrible. i crank it up in the mornings and it starts to rattle immediately. it sounds as if something is loose in the clutch area and is spinning around with it. it gets quieter as it warms up but it is there always. when driving it is there but you cant really hear it over the engine and everything else from inside.

i can control the noise with the clutch pedal. when pressed in to the floor there is no sound. when released it lets out some sound. however when im letting it out from a stop in gear there is a lot of sound as the clutch gets into the friction zone. this is not the transmission making any noises. if i hold my foot on the brake preventing the car from moving i still get the same sound as i let the clutch out in gear. the trans can not be spinning at this point since my foot is on the brake and the trans is in gear.

nothing has changed from before the noise to now other than the noise appearing. the clutch pedal still feels the same as it has for the 80k miles ive had this car. the car still drives and shifts great. the gripping of the clutch is great. i love the midrange and top end pull of the engine with the AL flywheel. ive put a couple hundred miles on the car since this noise has started.

thursday i pulled the trans and inspected everything. nothing was loose or showing any signs of irregular wear. the release bearing was slopping around against the PP springs, but the retaining spring/ring was still there and it was loose like this when i first did the clutch. the throwout bearing sounded normal and spun freely. the springs in the clutch disc were tight. however this was with the disc simply sitting on the counter. not sure if its possible for it to be distorting once its squished between the PP and flywheel allowing the springs to move freely. so just like the car drives perfectly fine everything looked perfectly fine.

i was thinking i need to replace the throwout bearing, but i don't have any money to simply throw at the car. since it appeared fine when inspected i couldnt justify replacing it without knowing for sure. also i spoke with the head clutch tech at Sachs. based on how the system works he said it cant be the throwout bearing. its under load when im letting the clutch back out. i actually stumped him so badly that he wants me to call him back when i figure out the problem.

on the way home the only thing i could think of is the clutch fork itself. with the slave disconnected the fork is pretty loose even when attatched to the throwout bearing. when the slave is in the trans it should be keeping pressure on the fork. when reinstalling the slave i did have to push it into the trans causing the rod to be pushed back into the slave. so my only thought is that even thought the slave is applying pressure to the fork its not enough and the fork is rattling around in there. this makes no sense to me though considering the pedal feels fine and i would think it would get slack if it was a hydraulic problem.

the car is a 96 formula. ive got a fidanza flywheel and a OEM replacement Sachs clutch. the pilot bearing and throwout bearing was replaced when i did the clutch. the hydraulics are all original with 145k on them. i did the clutch job easily 5k miles ago. this noise just started last week. no other issues other than the noise.

so im all ears as to any suspected causes.

thanks

[rocketman]

sounds like either the throwout bearing or the springs in the disc are getting disorted,is the disc bent.are you getting the balance points aligned,try tqing the pp down another ten pounds.also you should replace the the slave cylinder it may not be releasing fully.

[Steve68]

Sound like the input shaft bearings, you need to call the T-56 rebuilders and ask them about bearing noises in the older T-56, someone like that should answer all the "Q"'s

[WS6]

it shouldnt be the throwout bearing due to the fact that the LT1 clutch is a pull not a push, so when im letting the clutch put the bearing is under load and cant be rattling around in there. the PP springs are good and the torque on the PP is at 33ftlbs. thats what the service manual calls for.

i grabbed the input shaft while it was on the jack stand and it didnt move in any direction it wasnt supposed to. besides it cant be the trans due to the fact that when i have my foot on the brake and let the clutch out with the car in gear, i still get the noise. the trans cant be spinning at that point since my foot is on the brake.

what would be the symptoms of the slave not releasing fully? my pedal feels the same as before the noise started. i would have thought the pedal would feel differently.

thanks guys. i do appreciate the help. i just wish the odd stuff didnt always happen to me. makes me feel dumb that i cant figure it out. ive never had anything like this happen on any clutch change.

[Steve68]

I had a 88 BMW325is makes the same noise, sounds like bearings are rattling back and forth, check out LS1tech.com and check there boards, andlike I said try a rebuilder, they should be able to tell you,

[TitoJones]

That is a normal LT1 style T56 noise. You can replace every single part and it will come back. It is the throw out fork that is rattling around at rest.

Tyler

[WS6]

but mine rattles horribly when ive got pressure on the fork by way of the pedal. this is a very loud rattle. i can hear it inside my house when the car is in the driveway. this is much louder than the normal transmission noises. i expect some noises but this after 145k is new.

i appreciate all the help guys. i just cant not afford to throw parts at it and also i like to learn why things occur versus just what to fix to make it be quiet. if i could have i would have bought a new throwout bearing, clutch disc, and clutch fork while i had it apart.

thanks