Clutch is "chugging" when coming to a stop

[SkyBlast]

I need an idea on what might be going on with my clutch and how bad the damage to my wallet is going to be when I fix it.

My stock clutch was definitely not up to the rigors of the HPDE track days and went up in a big ass puff of smoke just after turn 11 at Carolina Motorsports Park in April of 2018. The stock clutch lasted 2.5 years and gave up the ghost after I added about 110hp to the car via FBO upgrades and tuning.

Pro Dyno in Fort Mill, SC installed a new McCleod clutch a few days later and I was back on track a week after that. It has been to 9 HPDE track day events since then and has done extremely well.

A few weeks ago I noticed the clutch start to chug a little when I pull up to a stoplight in 1st gear with the clutch pedal pushed all the way to the floor. It happens in reverse as well. The car is bucking a little while the chugging sound is happening. The chugging stops the second I take the car out of 1st gear and it doesn't seem to happen when I come to a stop in 2nd gear.

You can hear what I'm talking about in this video:

https://photos.app.goo.gl/DdqhveWcSdjHEqCr8

Note: The squeal you hear in the video is from my G-LOC track brakes. Those things make some serious squealing sounds when you come to a stop, but they will stop your car on a dime and hand you back a nickel and 3 pennies!

Some details:

Stock MT82 trans in 2015 Mustang GT w/ BG Syncro Shift II gear oil
McCleod RST twin disk clutch + steel flywheel + new throwout and pilot bearings on 4/12/2018

Any advice is appreciated. Have a great day!

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[Whitewalkers550]

sounds like the clutch isnt disengaging all the way, just had a similar issue with mine and culprit was the slave, might start there

 

[Grimmer]

+1.

I haven't had this issue yet, (knock on wood), but I've read several members here have. The consensus seems to be that it has something to do with the joint where the hose attaches to the slave or something to that effect. I also seem to recall them saying that the clutch and the brakes share the same fluid reservoir. I'm shooting from the hip on that one, so I could be way off. But if they do share, then it begs the question about leaking slave connections and eventual failure of both the clutch and the brakes should all the fluid leak out? Or maybe there is a dam in the reservoir that limits the losses across the two systems.

The other day I was getting a little suspicious about my clutch hydraulics getting weak, but I never got around to looking up the threads to check things out. It seems to have either resolved itself, or I was up in the night... For now, anyway.

You've got me thinking about it again, so there's another "to do" on my list.

 

[Whitewalkers550]

yes the brakes and clutch share the same fluid resi, mine wasn't leaking fluid but had something internal hanging it up and preventing it from having full travel

 

[Burkey]

Clearly the clutch isn’t fully disengaging. The synchros probably won’t enjoy that for too long.
I’d see if bleeding the clutch line offers any reward, also looking for potential sources of air ingress.
As others have said, could even be the master or slave giving up.
Bleeding the line and then finding the problem returning later would certainly suggest such a thing.
Something else worth trying, just for shits and giggles, is to pump the clutch repeatedly next time it happens and see if the clutch pick-up point moves at all.

 

[SkyBlast]

Thanks for all of your replies, guys! I'm taking the car back to the place that installed the clutch.. Dan (the owner of the shop) is curious what is going on. It's only had 9 track days and 13k miles since they installed it, which isn't anything for that clutch. I'll follow up with what they find out.

 

[SkyBlast]

ProDyno has the car now and has checked everything. Unfortunately they cannot find anything wrong, so they're going to send the clutch back to McLeod for them to measure and see if the pressure plate has become unsprung. Unfortunately this process takes a long time because of Covid-19. They're expecting it could take a month to get it back. Ugh.

 

[Whitewalkers550]

sucks to hear they didnt find anything and that it will take that long, once you do figure something out though let us know!

 

[SkyBlast]

I was hoping that it was something that could be adjusted at ProDyno.. but nope.

I absolutely will keep y'all posted. I am sure I won't be the only one to have this problem with their clutch, and hopefully it will help the community once we get the info.

He's going to give me the RMA number and a phone number to call so I can keep on them to get it done ASAP and get some info about what happened. I also need to send them that video so they can see and hear what was going on.

 

[SkyBlast]

A friend of mine suggested getting a new clutch and keeping this one as a backup in case this happens again. That's not out of the question... but what clutch would y'all recommend for a 465hp NA for the road course?

The tuner recommends a McLeod RXT which is a bit more sturdy than the RST is. Would going with an Exedy be better? What is everyone's experience with RXTs? Good? Bad? Ugly?

 

[OnThree]

Curious to hear what they say about your RST as my trans just started giving me problems too (I have a RST with similar mileage). Trying to chase down the culprit right now. Bled the clutch and brakes today to eliminate air in the system causing issues and no luck.

To answer your question on the RXT, I've heard the MT82 tends to break with those. I wouldn't install it, no clue on the exedy for these cars. Had one on my mr2 turbo back in the day it was great.

Good luck!

 

[SkyBlast]

Well, I'm considering going with the Exedy Mach 500 Stage 3 clutch (AKA Exedy Racing Stage 1). Anyone have any experience with this one?

I like that it should feel close to stock without the shuddering and chatter of the McLeod.

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