cstyles

Last weekend, was reversing out of my garage modulating the clutch when a loud metallic squeal occured, car stalled in gear, and clutch pedal got super weird and rubbery. Pushed clutch in, loud pop, clutch pedal stuck to floor but just a half inch of pedal play & clutch engagement I was able to put the car in 1st gear and limp it forward back into the garage. Turned off, gets towed to my tech next week to pull the trans and see what I broke. The car has 80,000 km / 50k miles and I believe this is the original clutch in the car now, so it was likely inevitable.

I've been researching clutch options for the 7.1RS, but most of what I find are threads and discussions related to the GT3 (non RS) upgrading to the RS4.0 LWFW clutch kit. I don't know much about these cars yet, I've owned Porsches for 10 years but this is my first 997 RS and just acquired it a few weeks ago. As the 997.1 RS already has a LWFW (albeit, not as light as the 4.0), I am not particularly interested in upgrading it further. I love the drivability of the car as-is, and this is a weekend street car with minimal track time that I plan to keep stock; what I want to make sure is that I select the right parts that will provide me the best reliability long term. But I don't want to put original parts back in if they are known to be weak and I could have selected something better from a reliability (not performance) standpoint.

I understand the 2007-2008 RS pressure plates were 'weak', and that it's likely what failed on my car. It looks like Porsche revised the part for the 3.8L RS and features 3 reinforcement straps rather than 2 straps on the 3.6L version.

- Can the 'upgraded' 3 strap pressure plate for the 3.8L be used in the 3.6L application? Is there a reason to use the 4.0L PP over the 3.8L PP? Or are they they the same part, and it's just the friction disc & flywheel that are different for the 4.0 kit?

- My tech is recommending the Sachs Performance clutch disc that crosses to the OEM 3.8L disc, which is the same Sachs clutch disc used in the high horsepower 997 Turbo "Sachs 2.5" kits - and which I used on my 997TT back in the day. Can any of you knowledgeable RS guys confirm that's a good choice for the 7.1 RS?

- If we find the flywheel has been damaged or otherwise needs to be replaced, is the Porsche OEM lightweight flywheel for the 3.6L the best option for replacement? Or are there alternatives I should be considering besides the obvious RS4.0 kit?

Thanks in advance guys!

Belinko

I think for the clutch it is a matter of opinion and also use application from OEM to Full race.

I wouldn't consider the clutch on the 7.1 a weak link. 50k miles on a stock clutch in high performance sports car (race car like) manual transmission car is very good with reasonably high clamping load. If you liked your OEM clutch (feel, noise, etc.) stick with it, replace it again in 50k miles. If you're interested in more performance (free revving) and willing to live with some added noise get the 4.0 RS setup.

JG 996T

id probably do 4.0 kit. probably dont need higher hp sachs plate, but then, why not?

powdrhound

Keep you flywheel and install the 4.0 disc and pressure plate. done...

cstyles

Yeah that is a great suggestion, just wasn't sure if that could be done on the 997.1 RS without doing the "entire" RS4.0 kit. But it looks like your suggestion would work just fine. I found this RS4.0 kit part list from an old thread documenting clutch failures, and the clutch disc & PP numbers both look to still be good numbers. We will use the clutch disc & PP from the 4.0 using this list.

These are from a post in 2011 though, if anyone happens to have the current RS4.0 pressure plate & clutch disk part #'s that would be much appreciated. All of the 4.0 complete kits I find online, none list the individual part #'s.

powdrhound

The 3.8RS and 4.0RS flywheels are the same part. The 4.0 version has a little more material machined from it near the perimeter making it 2lbs lighter with a lower MOI. They are 100% interchangeable.

cstyles

As you suggested though, and I am in agreement, I wouldn't change my 3.6L RS LWFW. The RS4.0 FW is slightly lighter but I am perfectly fine with the performance and free-revving nature of the stock LWFW on the 3.6L RS. I only want to change out the PP and disc, and want to ensure I use current parts that eliminate any weaknesses from the original 3.6L part designs. Case in point, it looks like the riveted 3.6L and 3.8L pressure plates can fail even with low miles, but the bolted RS4.0 pressure plate is bullet proof. Will use the 4.0 PP rather than the direct 3.6L RS replacement in this case. Cheers

Mvez

This the clutch you want, directly from Sachs. It's a slightly uprated Sachs Performance version, fits your flywheel. $988 Euros. Shows up to your house in 2-3 days via UPS. I have ordered countless Sachs performance clutch kits directly from them. Vendors do the same thing, then just mark them up. I use this clutch in my GT4, GT3RS, E30 M3, FRS, if they make one for a car I own, I buy it.

Skip the crazy pricing for the dealer 4.0 kits, these are the same, half the cost. If you look up the 3.8 and 4.0, they all reference the same clutch kit.

It blows my mind why nobody ever seems to order direct from Sachs. Saves a ton of money.

Porsche Performance Clutch | ZF SACHS 999764.999856 (sachsperformance.com)

Mvez

Here is the main link to look up any Sachs Performance clutch kit for whatever car you own, they have a specific one for the 3.6 RS

Online Store SACHS - Performance Clutch. Purchase. Drive. Satisfied. (sachsperformance.com)

powdrhound

Definitely not what you want for a GT3. Will work, but not really appropriate.

sirringo

Elaborate on that?

powdrhound

The 999.764 pressure plate is riveted and NOT bolted. The rivets are the weak point and give the pressure plate a lower rpm burst threshold compared to a bolted PP. This is the reason the old style 7.1RS plates had the rash of failures back in the day and this is the reason Porsche went with a bolted PP on the 4.0 version. The 999.764 PP is commonly used by turbo guys because those engines don't see the RPMs that a GT3 engine will see. The 764 PP can hold about 700 ft.lbs of torque due to its stiffer straps and this is why it's popular on the much torquier turbo motors. Unless you want a stiffer clutch pedal, there is no need for a PP that can hold 700 when a GT3 motors has about 300 ft.llbs of torque. The riveted 764 PP has also had some warpage issues in the past on heavily driven track cars. I have run into this with that plate but know of others that had the same issues.

Sachs motorsport does make a bolted version of the 764 PP which is designated as 487. It is basically a beefed up 4.0 PP which can hold 700+ ft..lbs of torque with a street disc (i.e 4.0 sprung disc). With a sintered 4-puck Cup disc, even more. This is a fantastic pressure plate I used to run in conjunction with a 996Cup 4-puck disc and a Cup flywheel on a 800hp race Mezger. If you have a built 4.1 7GT3 Mezger, the bolted 487 PP is the one I would consider due to its significantly higher clamping force.

With that said, I have run the 764, 487, and the OE 4.0 pressure plate. They all have their purpose. For a 7GT3, I would install the OE 4.0 PP and 4.0 disc. These are the way to go with either the RS or 4.0RS LWFW. Hope that helps..