Stiff GTM Clutch

[Dave 53]

Asking for a friend...

His GTM has a super stuff clutch peddle. Ridiculously stiff. My leg is soar just typing this.

LS3 and Mendeola transaxle.

He's tried different tubing and hoses.

The fluid in the Wilwood master cylinder almost immediately turns black. This has happened with 3 master cylinder replacements. It's on it's second slave cylinder.

Seems like it might be the clutch pressure plate? It is unknown what clutch is installed.

Looking for ideas on how to reduce the effort needed to press the clutch.

[beeman]

No leaks or other symptoms of a failing master cylinder? The 3/4" master cylinder in the kit is known to cause a heavy clutch, some have switched to a 5/8" to improve this.

[switta]

yes i switched to a 5/8 master wilwood part # 260-3372 , much better . i know this is a Mendeola but for a cheap slave cylinder for the g-50 is the 1986 BMW 325e autozone Part # 12116 just thought i would throw that in there for people that search for clutch issues .

[Dave 53]

No leaks. But, it has the symptom of the fluid very quickly turning black.

The car currently has a 13/16" master cylinder and 1/4" tubing. Seems he needs to get a smaller master cylinder, not bigger.

Any theories on why with the fluid keeps turning black?

[rolfer]

I think the fluid turns black because of something they use in assembly for the master cylinder and slave cylinder. Mine turned black as well.

[Shoeless]

I've got a 13/16" MC on my Mendy Stage 2 SDR-5 and my fluid is darker compared to my break MC as well. Pedal seems reasonable to me and glad I'm not the only one the fluid is darker.

Keeping in mind my Stage 2 likely has a different Tilton throw out bearing than what your friend may have. When I was setting everything up Ian recommended I go with a 13/16" MC.

[VRaptor SpeedWorks, LLC]

Every Mendy-equipped GTM that I've driven so far has a very heavy clutch pedal. As for the fluid turning black, I don't understand what's going on there as it does the same thing on every GTM we've built here, regardless of what transaxle was used. I have a car in the shop right now with a Mendy and yes, the fluid is black and the clutch is heavy. This car has the external slave on the RH side of the trans and the stock 3/4" MC. If memory serves, there's one or two GTMs with Mendy's that we attempted to switch over to a 5/8" MC in order to lighten up the pedal effort, and it would not move enough fluid to fully disengage the clutch, so we ended up going back to the 3/4". As Shoeless mentioned, some of the Mendy's have the external slave and some have the internal hydraulic T.O. bearing.....and in my experience, clutch pedal effort is heavy for both.

[crash]

If you want a lighter clutch pedal then go to the KEP double disc setup. We just did this on the FFR PDG GTM and there is a significant difference. I never really had an issue with the stage 4 single disc setup even after shifting it HUNDREDS of times almost non-stop during hours long endurance races, but maybe that is just me. The switch to the double disc allows you to use a stage 2 pressure plate which is much lighter and still maintain the same holding power as the stage 4 single disc. It is an easy swap as the double disc dimensions are identical to the single disc setup. We have put a cam in our LS3 and thus will exceed the single disc capabilities, so we switched over.

The fluid being black is common and ours is the same. I believe it has to do with the rubber material in the cup seal in the slave cylinder and/or the fact that most of the CNC slave cylinders I have seen are un-anodized and the aluminum housing may also be contributing to the coloring of the fluid. Totally normal though. I also see this in many regular OEM street cars with a clutch. I wouldn't worry too much about the fluid color.