The green genie: A proper Porsche 968 pressure plate
Tuesday, November 28, 2017
I'd had it.
I was through driving this 968. Aside from the looks, handling and power, the thing had one quality that kept me enduring the agony of rolling on: the drop top.
The Spaßmaschine's flaw wasn't that it cost double its purchase price and my own labor in mechanical rejuvenation, nor that its big-bore quartet fell short of the 993's orgasmic sextet. No, it was something much more trivial than that: the pressure plate — and it was my fault.
The 944S laid the foundation in my love of these transaxle Porsches. It possesses smoothness, a cat-like sophistication springing forward in every gear. A clutch requiring only the big toe to disengage was about 50 percent of the reason why such adjectives italicized every sentence spoken about our relationship.
Now, I had the final evolution of the four-piston transaxles, arguably the best of the series, with a clutch no better in feel than a '66 Dodge school bus. Despite having just less than 30,000 miles on this new kit, something was wrong — it had to come out.
Thankfully, access to the 968's clutch is much easier than its predecessors.
The Sachs clutch kit, while not cheap, has an enticing price over buying the individual pieces from Porsche. For around $675, the kit includes the friction disc, the pressure plate and the release bearing. It was only after installing the kit that I realized something didn't feel right; in fact, it felt identical to the one it replaced.
I had installed everything according to the shop manual, replaced the guide tube, fork shaft, needle bearings, pilot bearing, double-mass flywheel and used Olista Longtime 3EP lube wherever there was metal-to-metal contact. I'd also replaced both the master and slave cylinders, hydraulic hoses, pressure bled the system twice and made sure that the return spring at the pedal was properly adjusted to spec.
Was something defective? I had a suspicion, and color codes began clarifying things.
The 968 workshop manual has a page regarding the identification of the pressure plates between the 968, 964 and 993 with color markings; a smear of color on the outer side just above the "fingers." Green for the 968, blue for the 964 Carrera 2/4 and a red streak for 964 3.6 Turbo — the 993 has no color marking. It doesn't take a propeller head to figure out that any of these 240mm pressure plates are interchangeable between the models.
In Porsche's 1992 Service Information Technik for the 968, a factory service information manual, section 3-10 goes into detail regarding the pressure plate. It states that the clamping force of the 968 clutch is between 8,800-9,600 N (Newtons), which is equivalent to 1,978-2,158 lbf (pound-force) — a 2,200-pound pressure plate for argument's sake.
I leaned back, steepled my hands above my head and read on ...
"The assembled pressure plate is identical to the components used on the (911) Carrera 2 and 4 Model 1991. (As of Model Year 1992, Carrera vehicles feature a pressure plate with an increased contact force of 10,600 to 11,500N)."
So model year 1992-1994 964 Carrera 2/4, excluding Turbos, have an upgraded pressure plate with a slightly higher clamping force of around 2,300-2500 lbf. Not much of a significant difference in pound-force but probably just a bit stiffer. Based on this information, let's go back to color markings.
Interestingly, both the 968 and the 1989-1991 964 Carrera 2/4 use the same part number for the pressure plate — 964 116 027 90, which was superseded from 964 116 027 01 and 964 116 028 00 on both models. While they share the same number, technically the 968's marking is green while the 964's is blue to differentiate them. Maybe this logic applies to 1992-94 964 Carreras whose pressure plate has a higher clamping force and a different part number — 964 116 028 90.
We haven't discussed the red-striped 964 3.6 Turbo (no mention of the 3.3 Turbo in the manual), nor the 993 pressure plate without any markings because they simply don't figure into this equation — yet.
Here's the latest part number. Curious which company in Italy Porsche has contracted to manufacture these pressure plates — note the date.
Now, supposing your 968 needed a clutch say 10-15 years ago and you decided, "Hell, why buy it from Porsche when I can buy the Sachs clutch kit for less money? After all, Sachs (back then) supplied the pressure plates to Porsche; no sense in paying more for repackaged goods."
No one would be the wiser. Sachs sold you the kit, and in it was a pressure plate numbered 3082 213 131 (originally 3082 213 101/964 116 027 01). It had a green stripe on its face to assure you, visually, that this was indeed the correct pressure plate for your 968. In it went; same soft clutch it had from the factory.
This kit was used for pre-1991 (early) 964 Carreras, too. And while the part number stamped on the pressure plate might have been identical, they wore a blue stripe. It seems that, regardless of the stripe, if it had that part number, clutch depression was soft and very much like when it left the factory. This tells us that the clamping force must've been in the neighborhood of 2,300-2,500 lbf.
When I ordered the Sachs clutch kit three years ago, it seems that someone had changed the recipe. Had I done the research, I would've taken the right at the fork because what I've discovered may help should you be in the same predicament — before, and hopefully not after, the fact.
Why would I think differently? I've ordered Sachs clutch kits for other Porsches, and each performed with fidelity to factory specifications. But not this one.
The Sachs clutch kit I was about to rip out had a blue-striped pressure plate stamped with part number 3082 213 133, but the color code isn't worth a damn. After dozens of supersessions, it seems that Sachs had decided to make things easy and offer a one-size-fits-all unit, according to a few catalogs. All 968s, 964 Carrera 2/4s, 964 Turbo 3.3s and 993s are offered a kit with this pressure plate good for 3,100-3,300 lbf of clamping force.
The old "blue-striped" pressure plate 3082-213-133 included in the Sachs clutch kit for the 968.
The variable here depends on who the kit is purchased from or if it's new old stock (NOS). If you enjoy playing with numbers, plug that one into any search engine and see how many cross-references you come up with between Sachs and Porsche.
It was clear that a precipitous elimination of the softer pressure plate had occurred for dual-mass flywheeled Porsches of the '90s. While a handful of vendors make a distinction in offering two Sachs pressure plates for the 968 — 2,300-2,500 lbf or 3,100-3,300 lbf — there's no guarantee you'll get the former if ordering a Sachs clutch kit from other sources. As far as color coding is concerned, I've seen green- and red-striped Sachs pressure plates on eBay with part numbers long since superseded and probably NOS.
I'm through rolling the dice. Working on these cars is pleasurable, but doing a clutch job prematurely out of dissatisfaction is a waste of time and resources.
This and countless other examples cement the fact that buying replacement parts from Porsche is a wiser proposition. While buying the parts individually costs roughly $300 more, there's an assurance that this 968's clutch will feel the way it did when it left the factory.
The "proper" Porsche 968 pressure plate from Porsche.
The moment I finished torqueing the last of the slave cylinder's M8 bolts to 15 ft-lbs, I snaked myself from underneath, opened the door and depressed the clutch — what a difference.
Below are the parts and corresponding numbers for 1992-1995 Porsche 968s. I've purchased these from Porsche of Annapolis, one of my favorite dealers offering superb customer service and competitive pricing.
(Porsche warehouse locations valid as of this writing)
- Pressure Plate — part number: 964-116-027-90 (USA)
- Friction Disc — part number: 944-116-014-90 (Germany — four-week wait)
- Release Bearing — part number: 964-116-027-90 (USA)
- Pan Head Screws (nine needed) — part number: 999-510-015-01 (USA)
- Clutch Shaft — part number: 951-116-133-00 (USA)
- Needle Roller Bearing (two needed) — part number: 999-201-213-00 (USA)
- Clutch Guide Tube — part number: 944-116-087-01 (USA)
- Pilot Bearing — part number: 931-102-111-00 (USA)
- Olista Longtime 3EP High Pressure Grease — part number: 000-043-305-73
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