M3EvoBR

This is way beyond any simple resolution like bleeding the clutch.

Izzone

I should have saved the two I replaced

Based on my race shops findings its the pressure plate that goes bad. The bands bend slightly and then all the problems begin. Eventually the clutch brakes from the pressure plate being out of tolerance

Even the 4.0 clutch without the holes by the springs brakes, it cracks exactly the same

I thjnk if u drive ur gt3 likes race car buy a race car part, not the factory street car part

Jamie_GT3

What does your race shop recommend?

Jamie_GT3

So after quite a few calls and discussions with many a shop. It seems that when the clutch pack is decelerating (engine braking) or on the rev limiter then straps on the Pressure Plate are under compression. Being straps they are quite strong under tension, not so much under compression.

If only there was a way to eliminate them. Oh wait, there is billet pressure plates exist for just about every race clutch out there. Tilton, Sachs 2 and 3 disk setups etc... racing clutches don't have stamped pressure plates like street cars.

There is a dual disk setup for street cars that may fit the bill for us.

http://clutchmasters.com/index.php?m...=GetPage&id=20

take a look and discuss...

CRex

Another option is SPEC which has a number of ready made kits for GT2/3s...

http://www.specclutch.com/cars/Porsc...RS/2008/Single

Might be a good solution when our PP+4.0 clutch discs eventually wear out. After reading this thread and rethinking, I'm convinced that my clutch is slipping ever-so-slightly at WOT/straight line highway pulls. That's the only plausible explanation for an overheated gearbox on the highway. Track overheating I don't mind as much--over here we don't have defined sessions so we can pit in and rejoin anytime after cooldown. Not being able to come out of gear on the highway is altogether different and real annoying...

Jamie_GT3

I had heard SPEC helped BGB put a clutch together for Grand AM with a reinforced pressure plate. Was going to call them after the holiday...

mdrums

PDK in a Carrera based car aggressive DE seems to be ok with no over heating. Also some Carrera PDK that are club raced are fine. I have heard the Cayman with PDK can overheat. What have you noticed?

TRAKCAR

Ask John about the weight of his manual Cayman with 400HP and when he gets pricing to adapt a Cayman with GT3 brakes and engine upfit instead of the C2S parts bin upfit.

Jamie_GT3

That's a good point, the load on the clutch would be less than on our cars...

BGB Motorsports

Folks,

I was asked by someone to stop by and add any input. I haven't read this thread at all and can very well be repeating something someone has said already. With this sort of stuff, more information is better. If I repeat something or am wrong, I'm sorry. Don't yell at me though!

1.) Clutch woes have actually been a rather large pain for us this racing season and last.
2.) I would have a hard time believing that straps are failing due to heat. I have seen it happen but not on a unit like that. The missed shifts are causing the bands to weaken THEN break. It's a good thing that the bands accept the brunt of the missed shift, or else your motor would!
3.) I have experienced continued heat woes which as you all have found out, changes the finger resistance which changes the clutch engagement point which requires clutch stop adjusting and if it gets bad enough, becomes near impossible to shift. This is effect of the heat. For those of you that are removing undertrays that help direct air up to the bell housing, you are making matters worse. Running a naca duct and some tubing up to that area and helping the slave line that is coiled for a reason (heat dissipation) to have more cooling.
4.) While an argument can be made that an aluminum flywheel will retain more heat than one with twice as much metal to dissipate the heat, I can't imagine it's the sole cause. It could potentially be too much added heat and it could be the tipping point.
5.) The more pucks the more heat.
6.) If the throwout bearing has crappy grease in it and doesn't retain grease well, that will make matters worse.
7.) Plastic hydraulics that exist on the 997.2 don't help matters. The clutch slave and master are plastic on a 997.2 and on the 987.2. That is just an additional thing to make matters even worse.

Ultimately you guys should be getting more life out of your clutch kits, but at the same time, you're spinning these motors to 9K RPM, correct? We really are at the rotational capacity of a lot of this stuff since we're spinning it to higher levels, etc.

Sorry if I have repeated anything but we have had our own clutch problems and I have chased everything.

If you want to help yourselves the most, as my old mentor Martin Meade at Girodisc used to say, you MUST exhaust all cooling options known to you. He used to say "don't call me until you have as much brake cooling as the rule book will allow." I know it might sound like overkill for street cars but if you want to track your cars and have stuff last longer, you need to do a few things.

These cars are unbelievable machines from the dealer but we're asking more of them than we would if we were just street-driving them. They may be "race inspired" but you're still beating on your street cars.

TRAKCAR

I'm up for that.

Other than that;
-Flush clutch
-New throwout bearing?
-Maybe at this point I should just throw in a new PP and clutch.

Jamie_GT3

So it might be a compounding issue.

Slave heats up, engagement changes, we keep forcing it to shift causing permanent damage to the diaphragm and potentially the PP?

If you have a naca duct setup can you get a picture?

Are there metal slave cylinder options?

Have these upgrades helped your failures?

I was looking at a multidisc setup with a billet PP to strengthen the setup and remove the centering straps from the equation.

BGB Motorsports

I really don't want to jinx ourselves but now that that we have added air to the bell housings, failures or changes in the clutch behavior haven't returned. We did however have an issue with a pressure plate that must have been shocked/overheated/whatever, but no matter what we did, we couldn't fix what felt like a changing clutch point. The fingers were getting hot and the point was changing, just like you guys experience. We threw that kit out, put a stock kit in at the Glen last weekend and after 3 weekends, no clutch issues finally. Point being...YES...sometimes some equipment can fail because its soft/shocked/overheated/to the point of excessive over-heating/bigfoot touched it/Lochness Monster licked it/Elvis fingered it/whatever. Stuff wears and you replace it and you're fine but we can't NOT find out what caused it.

An overheating slave can begin to behave like a clutch that needs to be bled but the damage would only be if the clutch's stack height were terribly wrong. If so, your pedal could suck past center and over-extend, but even still, every time we have swapped hydraulics, thinking it was hydraulics, it's the pressure plate failing. 9 times out of 10, you start chasing a clutch bleed only to find out the plate is falling apart. You would be correct though that if you had a slave failure you would maybe hurt the PP but I don't know. I feel as if that's one of those things I can be gullible and convince myself of happening that someone smarter would say can't and I'm by no means a clutch expert and don't consider myself a knowledgeable person on that front.

We have always discussed metal slave options but I don't know why we keep giving up. I think that the 997.1 parts don't bolt directly to the 997.2 trans?!? Hole patterns are different?

If I didn't mention earlier that running 4 pucks as opposed to 6 pucks or maybe a material that generates less heat, I should have.

Heat is the enemy of all street-stock cars. Remember this, if nothing else. The 997.2 has a return to the reservoir that didn't exist on the 997.1 for a type of self bleeding when you follow the factory clutch bleed procedure and it seems to work really really well.

Do some analysis and tell me what percentage of the clutch failures are from guys that are at places like Buttonwillow, Sebring, Homestead, VIR in the summer, etc etc etc...I bet guys in the northeast or guys in the mid-west don't have these issues, even though they run half the year. The data would be a bit flawed because of the seasons, but you see where i'm going with this. Most simply, at 90 degrees ambient temperature outside, you are driving a car at 8/10ths that's 3300 lbs and has no ducting and for all intents and purposes, is a little piggy trying to behave like a race car. Given that I don't get to work out because we live on the road during the summer, it would be like you asking me to run a mile in the summer with no training. I would have a coronary.



Here's the thing...a new PP and clutch will resolve it, but it's not going to stop it from happening again after a bunch of events. So I feel like we're giving up when we do that, but we had to all last year when we kept cycling 997.2 clutch kits through the GS cars. None of the 997.1/997.2 GT3 stuff will work with the Aisin 997.2 drivetrain so we didn't have that to go back to.

A kit from a company like Spec Clutch that is for this MY car, etc., will be perfect. But if you are trying to stick with OE parts, then I think you need to do the following:

1.) Bleed / Flush the clutch (if you aren't using Castrol SRF in your car, you should be) and remember that when you're heating the bejeezus out of your brake fluid, your car needs that fluid for the clutch! If you have no brake ducts, SHAME ON YOU!
2.) Re-pack the throwout bearing with some fancy high temp NEO grease.
3.) Get some air to the slave.
4.) If your car has plastic hydraulics for the clutch (pardon my ignorance, but I don't know if it's aluminum on a GT3 or not), sourcing an aluminum would be better but these aren't off-the-shelf pieces. I would bet PCAG uses racey hydraulic slave parts on the GT3.
5.) Put a new clutch kit in it 1 more time and do steps 1-4, they don't cost much (steps 1 - 4 i'm talking about - I don't want to know what you guys pay to replace a clutch from some shops like ours in the real part of the world.

TRAKCAR

I'm sure others here have more answers but ill try to get max air to it.
I'd say oem is $2500 in parts plus labor. Maybe 3 -5 hours?
Call it 3k for all new bearing, pp, clutch plus bleeding clutch etc.

I'd say with carefull shifting and lots of preventive maint the 3.8 lasted 14k miles, half of them track, than I put 4.0 parts in and the car is still going at 24k miles.

My 4.0 bought with 3600 miles now has 7100 and starts to show symptoms.

Even without extra cooling for most DE drovers it only needed once every year to 2.

Soo, what about a Cayman with 475hp.

Ur20v

I have said elsewhere, get a tank hole cutter drill two holes- one each side. one side press fit a suitably sized plastic elbow pointing down hill to stop grit, stones and water entering, the other side, same elbow with flexi ducting pipe to a NASA duct cut into the gearbox under tray and bingo a cooled clutch, flywheel, slave and thrust bearing. 2" holes should work fine.

Jay