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Actually the 4.0 is the chosen disc in the updated Sachs 2.5 kit. There’s about a 120 dollar difference. What holds torque is the pressure plate. Disc material has a play as well but I don’t see it being any different between the two. I could be wrong but that is what I am trying to find out.
The Genuine Porsche 4.0 disk is Sprung the Sachs 2.5 has a CNC'd billet hub and Rigid with no spring. You cannot use the 4.0 disk with a dual mass flywheel.
The turbo fits the dual mass flywheel, the 4.0 fits the single mass. The 4.0 is rated to handle more power at higher RPM.. Moot point with the turbo (don't see 9K)
I asked Kevin the same question yesterday after I realized I bought the 7.2TT disk instead of the 4.0 RS disk. I probably did it by mistake when I bought it several years ago in anticipation of an early clutch death after installing Kevin's stage 1 tune. Well, the stock clutch lasted wayyy longer than I would have expected. But, I haven't tracked the car and I'm not the clutch-dropping launch type. Now that I'm approaching 70k miles, I have to get really serious about a clutch replacement.
I hated the idea of not using a brand new disk and buying the 4.0 RS disk. So, I pulled out my parts and did a test fit today. Good news... It fits my 764PP and single mass Aasco flywheel perfectly. No interference between the (rather long) splined clutch hub and the single mass flywheel. Others might know this, but the gearside of the clutch interferes with throw out bearing UNTIL you torque down the pressure plate. That had me concerned at first fit up, but I guess it is just the nature of pull type clutches with diaphragm springs.
So, fit looks to be fine... And guess what? Checking online pics of the 4.0RS clutch reveals what appears to be the exact same design, with the "long nosed" clutch hub. Add to that... Both designs use the same "friction" material, indicated by the same "xxxxxx2358" stamped on the friction surface. I know pressure plate determines max torque holding, for the most part, but confirming the same friction material adds confidence.
The only unknown difference is the strength of the clutch hub springs. Those could be different, but look to be the exact same (same diameter, same number of coils). I'm not sure how critical the spring tuning would be (to minimize power pulse vibration transmitted to the tranny), but neither disk is intended for the 996TT and both engines are 6 cylinder boxers. So, that probably isn't a critical difference. The critical design aspect is springs need to be strong enough not to fail under high torque (torque loads exceeding spring yield strength). I can't imagine that the 997.2TT torque is any less than the naturally aspirated 4.0RS. So, we're probably good there.
Okay... Who cares if the disks are functionally equivalent? Well, the 997.2TT disk is $100 cheaper than the 4.0RS disk.
Flywheel side of the 4.0RS disk. Note the long nose. Pressure plate side of the 4.0RS disk. Look close and you can see the part number. Flywheel side of the 997.2TT disk Pressure plate side of the 997.2TT disk. Check the part number in the pic.
That was exactly why I was curious was bc of the pricing.
Purchase both and compare them side by side to get an honest comparison for yourself. You can always return the one you don't end up using. Lots of opinions and advise out there by so called experts which may not always be factual or true.
The latest 997GT3RS 4.0 clutch disk has a new part number (ending in .92) AND differs in the appearance to the photo's above. The new disk has been out for about 6 months now and is made in Slovakia AND differs from the rivet heads pictured on the 997.2TT and 4.0 disk. The 4.0 disk has a inner and outer spring similar to previous 4.0 ltr disks, the springs are a little darker. Visually different vs the above pictures both 997.2TT and RS 4.0
It is my opinion that the 997GT3RS 4.0 disk is stronger and has a slight redesign (rivets, springs and top metal hat/stamping) and new manufacturing plant vs the old disk. This disk was designed for a LWFW installation. The 997.2TT disk looks very similar in design. But I would strongly doubt that it's a clone and part number change only vs the 4.0 disk. The 997.2TT disk is designed to run with the dual mass flywheel. The previous 996/997GT3 (non GT3RS 4.0) disk have a shorter nose vs the 997.2TT disk. For track use and for a higher output engine I'd recommend the 4.0 disk paired with a LWFW.. For the dual mass flywheel. I'd just run the 996/997GT2 disk.
If you go to my website you can actually see the difference between the older 4.0 and the newer 4.0 which is pictured under my 4.0 plus kit. http://ultimatemotorwerks.com/clutch.html
The latest 997GT3RS 4.0 clutch disk has a new part number (ending in .92) AND differs in the appearance to the photo's above. The new disk has been out for about 6 months now and is made in Slovakia AND differs from the rivet heads pictured on the 997.2TT and 4.0 disk. The 4.0 disk has a inner and outer spring similar to previous 4.0 ltr disks, the springs are a little darker. Visually different vs the above pictures both 997.2TT and RS 4.0
It is my opinion that the 997GT3RS 4.0 disk is stronger and has a slight redesign (rivets, springs and top metal hat/stamping) and new manufacturing plant vs the old disk. This disk was designed for a LWFW installation. The 997.2TT disk looks very similar in design. But I would strongly doubt that it's a clone and part number change only vs the 4.0 disk. The 997.2TT disk is designed to run with the dual mass flywheel. The previous 996/997GT3 (non GT3RS 4.0) disk have a shorter nose vs the 997.2TT disk. For track use and for a higher output engine I'd recommend the 4.0 disk paired with a LWFW.. For the dual mass flywheel. I'd just run the 996/997GT2 disk.
If you go to my website you can actually see the difference between the older 4.0 and the newer 4.0 which is pictured under my 4.0 plus kit. http://ultimatemotorwerks.com/clutch.html
kevin, looking at your website link, is there an overall weight difference between the GT3/Turbo 4.0 kit and the GT3 lightweight flywheel kit?
what is the weight difference between those and the stock dual mass set up?
can both be used with the stock slave accumulator set up?
The 4.0 clutch kit is around 3 to 4 oz heavier due to the larger steel nose.
The LWFW kits are typically 15 lbs lighter!
YES, you can use the stock hydraulic assisted slave!
10-10-2018, 08:35 AM
What is the difference between the 997 4.0rs and 7.2TTclutch disc?
