South Bend Clutch Slipping

[DWR-DSM]

I put my GSX on the dyno and I'm having clutch issues. I have a new ACT flywheel, a South Bend Clutch, and when the tuner gets to 13psi on a 5557 about 3500rpms the clutch slips every single time while in gear. Stage 3 TMZ tranny, new oem tb, new slave n master.

Any thoughts?

 

[Dsmkauai]

How many miles on the clutch? Was it properly broken in?

 

[kchaazz]

If its broken in and properly, Id say its likely preloaded from having the adjustment rod out too far on the clutch master cylinder. Can you push the clutch fork toward the driver side of the car by hand? You should be able to do this. Id check the adjustment first, its by far the easiest thing to check, and you can correct the problem- if this is the problem- in minutes.

 

[DWR-DSM]

How many miles on the clutch? Was it properly broken in?

Im assuming I need more miles on it. So I started driving it around town more to get more miles on it.

If its broken in and properly, Id say its likely preloaded from having the adjustment rod out too far on the clutch master cylinder. Can you push the clutch fork toward the driver side of the car by hand? You should be able to do this. Id check the adjustment first, its by far the easiest thing to check, and you can correct the problem- if this is the problem- in minutes.

It grabs and releases fine as long as I dont get on it hard. Im going to give it another 1-2 weeks of break in. I have a feeling it could be the ACT flywheel. If I see no difference after about the 2 weeks Im going to take the tranny off.

 

[kchaazz]

So, how many easy stop and go miles did you put on the clutch before putting the torque to it on the dyno? Also, it would definitely be good to check the flywheel step height as well, as the step being too shallow or too deep will prevent the pressure plate from being able to put full pressure on the disk and will cause slipping.
You say that the clutch engages and disengages fine, but without checking the fork as I have suggested, you dont know if the clutch is being preloaded from having the adjustment rod on the master cylinder out too far and this is very easy to check and correct. Where in the pedal travel is the clutch engaging and disengaging? If its very close to the top, AND you cant push the fork on the tranny to the driver side of the car, then the clutch is preloaded for sure, and all youve got to do to fix this is to bring the adjustment rod in a quarter turn at a time until you can push that fork. After doing this, you will have a bit of freeplay at the pedal- just a little- and the clutch will be manipulated right around the middle of the pedal travel. IF the master rod is out too far, you block the bleeder in the master, and fluid cannot return to the reservoir, it is effectively trapped in the master and slave bores and the line in between and the clutch will not only slip, but as the fluid heats and expands, the clutch will be preloaded more and more and the slipping will become worse and you will even destroy the pressure plate fingers and tob.
Please just try checking this before dropping the transmission or driving the car cause its very easy to fix like I said and itll save you so much trouble. If its not the problem Ive described, then drop the transmission.

 

[lil corb]

Also what kind of SBC clutch is it? Organic? kevlar? etc...

 

[twicks69]

He has a full Kevlar disk being utilized with a media blasted pressure plate, and the flywheel is NOT media blasted.

I already instructed him to put considerably more mileage on it as it is simply not broken in yet.

 

[DWR-DSM]

Tim you was right. I put 900-1000 miles on the clutch. Held 22.2Lbs of boost, 404awhp, 320tq with not one slipping issue.

 

[twicks69]

Good to hear. told you so dude, the Kevlar material simply needs a longer break in period before dyno-tuning it or beating the crap out of it to properly bed into the pressure plate and flywheel. The media blasting of the pressure plate and flywheel help shorten break-in period, but it is by no means a drop-in-and-go clutch material. If people wanted that, they should go to a Feramic or Ceramic material or back to an organic disk. There are drawbacks to each one as well including streetability, durability, lifespan, and temperature range.

 

[ceedawg]

Good to hear. told you so dude, the Kevlar material simply needs a longer break in period before dyno-tuning it or beating the crap out of it to properly bed into the pressure plate and flywheel. The media blasting of the pressure plate and flywheel help shorten break-in period, but it is by no means a drop-in-and-go clutch material. If people wanted that, they should go to a Feramic or Ceramic material or back to an organic disk. There are drawbacks to each one as well including streetability, durability, lifespan, and temperature range.

So before I tune my car how many miles should I put on my kevlar clutch before it goes on the dyno? Guess i will have to put back in the 660,s while building the motor with the present Aem ems tune I have. The fic 1450's will have to sit on the side until clutch break in.
Oh forget it I see,about 1000 miles.. Dont know how I missed that!

 

[silvreclips]

1000 miles is a pretty safe bet, Kevlar is a great material and will give you a super smooth driving clutch if its broken in properly. Beating on it and slipping it to early can glaze the facing and give you a very chattery clutch engagement.

 

[UofACATS]

1,000 mile break-in would probably be sufficient for everyone, however it's important to remember it's not about the quantity it's about the quality. Break-in miles means actively using the clutch, so every persons total number of break-in miles will differ as the environment dictates. I presume it's common knowledge, however I've been seeing a lot of "SBC slipping" threads lately and most have been low break-in-mile issues.

As a data point, I broke in my SS/TZ for 600 miles and it's been flawless. I'm in AZ which is moderately spread out but I purposely took the routes with the most stop and go because waiting for a clutch to break in is an exercise in self discipline, especially on a new setup you're dying to test at WOT. Just remember, going WOT too early and glazing the disc means delaying break-in even further.. So find your zen, meditate, or do yoga as necessary and get it broken in properly