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Today I received my Spec stage 2 clutch. I ordered an OE setup for comparison. I opened the Spec box and was quickly disappointed. It's going right back.
Clutch discs:
It was very clear the first clutch I examined disc was off center. The 2nd disc appeared better but it was noticeably off center too.
I grabbed a caliper and they were both 0.5mm off center anywhere they were measured. I checked a set of OE discs and they were dead centered.
Compared to the OE discs the Spec units are noticeably heavier, this is a large part of the inertia that the synchros have to over come and I think it would turn the weak synchro's in the early 5 speeds to mush quickly.
Pressure plate:
It's off center too! It appears to be a stock Sachs modified with extra thick peripheral spring tabs with the pressure plate machined down in order to thin it. The Spec discs are slightly thicker than OE so the pressure plate was machined.
I noticed it had a tremendous about of material removed from one side of the clutch pressure plate. That seemed odd because the OE Sachs unit had a very small amount of material removed for balancing.
Why did Spec have to remove so much material to get it to balance out? It was striking to see but the pressure plate was clearly off center. At this point I stopped looking.
I check the Sachs OE pressure place and it was dead center.
There's only 1 word for this Spec clutch... Junk.
I have no idea if all these off-center conditions would produce any issues but I'm not going to be the person to figure that out.
Both disc were visibly off center.
Here's how they stiffen the pressure plate, thicker peripheral springs. In the process of modifying it the they ruined a OE Sachs unit.
Pressure plate was off center by about 1mm
This pin was clearly bent, leading to the off center condition for the pressure plate.
Starts out as a Sachs unit. look how much material needed to be removed to balance. Numbers on the fingers match the OE Sachs unit number for number.
Spec clutch disc set weighs 1.3 Lbs more. No good for the synchro's.
Last edited by icsamerica; 10-12-2020 at 09:54 PM.
Shocking. No one has ever had one of these clutches "chatter", have they?
BTW....the "early" synchros are not fragile....they are extremely robust. Externally lubricated and cooled. Very positive shifting, with instant feedback if you "missed" a shift.
The issue with these synchros has always been the same...they work perfectly, until the first dual disc clutch got replaced or the hydraulic system got touched.
And since almost no one knew what needed to be replaced, knew how and what to use to lube the parts, didn't know or understand how to adjust the clutch, had no idea how to modify the replacement clutch master, didn't understand how to route the new blue hose, and couldn't properly bleed the system, the synchros then took some severe abuse.
5,000 to 10,000 miles later, the synchros were junk (along with reverse gears.)
And then, "mechanics" who had no idea of what they were looking at, or what needed to be replaced, tried rebuilding them.
That rarely worked....and 5,000 miles later, the transmissions needed to be rebuilt again....because they were "crunching" again, when shifting. Of course, the owner was pretty tired of this....and tired of paying for it, so they drove around with "crunching" synchros until really terrible wear occurred.
That's what 85% of these transmissions are doing, at this time.
Everyone blames the synchros, when the issue was the idiots, all along!
Shocking. No one has ever had one of these clutches "chatter", have they?
BTW....the "early" synchros are not fragile....they are extremely robust. Externally lubricated and cooled. Very positive shifting, with instant feedback if you "missed" a shift.
The issue with these synchros has always been the same...they work perfectly, until the first dual disc clutch got replaced or the hydraulic system got touched.
And since almost no one knew what needed to be replaced, knew how and what to use to lube the parts, didn't know or understand how to adjust the clutch, had no idea how to modify the replacement clutch master, didn't understand how to route the new blue hose, and couldn't properly bleed the system, the synchros then took some severe abuse.
5,000 to 10,000 miles later, the synchros were junk (along with reverse gears.)
And then, "mechanics" who had no idea of what they were looking at, or what needed to be replaced, tried rebuilding them.
That rarely worked....and 5,000 miles later, the transmissions needed to be rebuilt again....because they were "crunching" again, when shifting. Of course, the owner was pretty tired of this....and tired of paying for it, so they drove around with "crunching" synchros until really terrible wear occurred.
That's what 85% of these transmissions are doing, at this time.
Everyone blames the synchros, when the issue was the idiots, all along!
Spec was boxed and shipped back. OE Sachs items will have to do for now.
Greg, I understand what you're saying, I just did an early clutch and the pressure plate adjustment is quite simple but the do'er needs to be in the know and I can see how many untrained Porsche mechanics factory or otherwise may not have known. I used the info found on the forum to attached a ratchet strap to the clutch arm and carefully adjust it during the clutch job process. Went from dragging badly to zero drag, astonishing difference. I can easily envision a mechanics eyes glazing over during a explanation, then when the clutch drags they'll exclaim "928's suck". I've been there, that and a bursted brake hose are why I do all my own work. Reinforced by the fact that last time I brought my car for an alignment they did it carfully right to my spec, but left the tie rods loose so I had the privledge to have done a track day with loose tierods.
Bad mechanics not-withstanding...It's also true that the later BW style synchro's are more robust for using the car as Porsche intended single clutch or not. There's a reason Porsche upgraded the 928 and the 911 in 1987 to the BW syncho's. What could the reason be? price? No... they're just better so less customer complaints. No way was Porsche going to allow a Camaro to shift better than a Porsche. I'm sure an early box can be made better and the best it can be with careful rebuilding, proper techniques and proper clutch setup.
This reminds me of the Small block Chevy guys who spend 10k rebuilding a motor with all type of pricey internal go fast parts to make 500HP. All the while a 500$ junk yard LS will make 500 HP with basic bolt-on parts for about 3k and will run smoother, drive better, make more average power, and wont leak oil. Why...it's just a better design to start. I've done both but as I get older I'm doing a lot less of the former. I guess the difference in this case is that you can blindly throw a rock and hit a LS engine, not the case for the later 928 transmissions.
Personally speaking I like the feel of the BW syncho's, I presently have 3 different cars that use them. That said I'd also like to own an early no spoiler 5 speed car again that shifted well enough. It would be more from a rebuild challenge / redesign perspective though. Kind'a like this....yesterday me and my family walked to the top of an abandoned ski slope, difficult, unnecessary, had better things to do, but a great sense of discovery and accomplishment when at the top.
There will always be people that like the shifting of they early transmission and vinyl records,
That said my next project... a turbo I6 Jaguar, will use a Tremec T56 magnum, I don't know what synchro's they use in those units but those transmissions are stick magic.
Last edited by icsamerica; 10-18-2020 at 03:45 PM.
This problem could have easily been eliminated had Porsche put an inspection door on the lower bellhousing. Not designing it to be adjusted in situ was a horrible oversight IMO.
Spec was boxed and shipped back. OE Sachs items will have to do for now.
Greg, I understand what you're saying, I just did an early clutch and the pressure plate adjustment is quite simple but the do'er needs to be in the know and I can see how many untrained Porsche mechanics factory or otherwise may not have known. I used the info found on the forum to attached a ratchet strap to the clutch arm and carefully adjust it during the clutch job process. Went from dragging badly to zero drag, astonishing difference. I can easily envision a mechanics eyes glazing over during a explanation, then when the clutch drags they'll exclaim "928's suck". I've been there, that and a bursted brake hose are why I do all my own work. Reinforced by the fact that last time I brought my car for an alignment they did it carfully right to my spec, but left the tie rods loose so I had the privledge to have done a track day with loose tierods.
Bad mechanics not-withstanding...It's also true that the later BW style synchro's are more robust for using the car as Porsche intended single clutch or not. There's a reason Porsche upgraded the 928 and the 911 in 1987 to the BW syncho's. What could the reason be? price? No... they're just better so less customer complaints. No way was Porsche going to allow a Camaro to shift better than a Porsche. I'm sure an early box can be made better and the best it can be with careful rebuilding, proper techniques and proper clutch setup.
This reminds me of the Small block Chevy guys who spend 10k rebuilding a motor with all type of pricey internal go fast parts to make 500HP. All the while a 500$ junk yard LS will make 500 HP with basic bolt-on parts for about 3k and will run smoother, drive better, make more average power, and wont leak oil. Why...it's just a better design to start. I've done both but as I get older I'm doing a lot less of the former. I guess the difference in this case is that you can blindly throw a rock and hit a LS engine, not the case for the later 928 transmissions.
Personally speaking I like the feel of the BW syncho's, I presently have 3 different cars that use them. That said I'd also like to own an early no spoiler 5 speed car again that shifted well enough. It would be more from a rebuild challenge / redesign perspective though. Kind'a like this....yesterday me and my family walked to the top of an abandoned ski slope, difficult, unnecessary, had better things to do, but a great sense of discovery and accomplishment when at the top.
There will always be people that like the shifting of they early transmission and vinyl records,
That said my next project... a turbo I6 Jaguar, will use a Tremec T56 magnum, I don't know what synchro's they use in those units but those transmissions are stick magic.
For pure street use, the Borg Warner design synchro is definitely easier to shift....there's absolutely no question of that.
And as the "Porsche Sports Car" evolved to a very "high end" (more expensive) GT style cars, Porsche felt the need to accommodate "softer" drivers.
Past that, these synchros are not nearly as good, for several reasons.
Of course, anyone that "grew up" driving Porsches, since the 356's, got used to the feeling of the Porsche design synchro and appreciates the "feedback" from this style synchro.
Unless one is a complete idiot, there's absolutely no possible way to not know if you've just shifted the transmission into the wrong gear......the feedback from the synchro into the gearshift lever is....radical. No one ever would release the clutch, after they felt the car "go into" the incorrect gear.
I really enjoy this feeling and really enjoy the feedback that will never fail to inform you that you just put the transmission into the wrong gear!
My first Borg Warner transmission was on my RS America, which I immediately started taking to the track for time trials. My co-driver was a far better driver than I was and could pull way more "G's" through corners, which in those stock cars, shifted the entire engine and transmission to the side. (Actually, the engine and transmission continued in the original direction as the chassis changed direction.) This changed the location of the gearshifter, in relationship to the engine and transmission. (Porsche completely redesigned the front transmission mount for the 993's, for this reason, alone.) And because there was absolutely zero feedback from sticking a Borg Warner style transmission into the wrong gear, we blew that engine up (and blew up the clutch pressure plate) 3-4 times.....pretty quickly. (Once, the exploding pressure plate virtually sawed the transmission case into two pieces.) Once we identified the real problem (which took a bit of time and effort to figure out and solve), we made some mounts that kept the transmission and engine going the same direction as the chassis. This ended the engine and clutch explosions. However, my point is the same....if these transmissions still had the Porsche design synchro, we would have never had an engine or clutch failure.....maybe some broken wrists from the gearshift beating us senseless, but we would never consider letting the clutch out and never have had an "over rev" engine/clutch explosion!
Additionally, the older "Porsche design" synchro is externally lubricated...and sloshing continuously through fresh, clean, cool gear oil. The Borg Warner transmissions have the synchro friction surface internal and are very difficult to get cool, fresh gear oil to. Porsche partially repaired this problem by adding internal oiling to the synchros in the 993 version of the G-50 and by adding a spray system into the GTS transmissions. This "kinda worked" for street cars, however, we could never get enough lubrication to the track cars for this to solve the overheating of the friction surface and the resulting galling of the gear teeth cone on the gear. Even in short 45 minute IMSA sprint races, most of the gear teeth cones and synchros would be destroyed after even these short races and we had to replace many, many gear sets and steel synchros after each event. For the 12 hour and 24 hour races, we would lecture the drivers about slowing their shifting down and taking it easy on the synchros, but after an hour or so, each gear would "crunch" and the gear teeth cones (and synchros) would all be trash by the end of the race.
Of course, this would not have been an issue with the early design synchro.
I drove my '77 911 with a 915 transmission in it for 15+ years on the race track. I never replaced a single synchro or gear....hundreds and hundreds of hours. I did "blow up" several clutch discs, right after Sachs went to the non-asbestos clutch lining (which was very brittle and did not like quick clutch action, combined with high horsepower), but this was not the transmission's fault.
I hope this puts the "inferior" early synchro design in better "light".
Like most threads this one is off track a-bit, that's OK becasue the comment that I made about the heavier spec clutch disks making mush out of the early synchro's is just an opinion based on reason and experience with a few early cars. Most early 5 speeds are 35+ years old at this point and are marginal if driven, unless carefully rebuilt. In either case If I had original 5 speed, or went through the expense of rebuilding one I wouldn't stress it and temp fate with a heavier clutch disk. I just put the weight out there so some one could avoid the mistake of buying a spec clutch.
Early synchros being better for the track.. somewhat pointless distinction... the VAST majority of 928's with 5 speeds are only street driven where the later synchro's are far better. As for racing, I might suggest, If a driver is using the Synchros to the point of overheating them, then learning to rev match better and perhaps use a cooling technique would help. I know both are easier said then done but most contemporary race cars suffer from over heated diffs and have or need oil coolers. From a limited race perspective I see heat as a problem that needs to be managed / dissipated in most cases.
I can imagine mod'ing the BW synchro's to cool well enough. That would be more 'do-able' than getting the earlier synchro's to shift like the later one becasue of fundamental design and materials.
Romanticizing the early transmissions is cute and taps into nostalgia and the persistent idea that old things are better then new things... I dont see it that way. I appreciate old things for what they are and I understand the allure of simpler times gone by. I have lots of old things, Juke Boxes, old cars, pachinko machines, pinball machines etc. I have new stuff too, newer cars, hybrids, VR and modern game consoles. No comparison. It's for this reason my next race build is getting a turbo and a T56 Mangum which can be power up-shift'ed with an ignition cut. After that a DCT or electic.
Last edited by icsamerica; 10-21-2020 at 12:40 PM.
Like most threads this one is off track a-bit, that's OK becasue the comment that I made about the heavier spec clutch disks making mush out of the early synchro's is just an opinion based on reason and experience with a few early cars. Most early 5 speeds are 35+ years old at this point and are marginal if driven, unless carefully rebuilt. In either case If I had original 5 speed, or went through the expense of rebuilding one I wouldn't stress it and temp fate with a heavier clutch disk. I just put the weight out there so some one could avoid the mistake of buying a spec clutch.
Early synchros being better for the track.. somewhat pointless distinction... the VAST majority of 928's with 5 speeds are only street driven where the later synchro's are far better. As for racing, I might suggest, If a driver is using the Synchros to the point of overheating them, then learning to rev match better and perhaps use a cooling technique would help. I know both are easier said then done but most contemporary race cars suffer from over heated diffs and have or need oil coolers. From a limited race perspective I see heat as a problem that needs to be managed / dissipated in most cases.
I can imagine mod'ing the BW synchro's to cool well enough. That would be more 'do-able' than getting the earlier synchro's to shift like the later one becasue of fundamental design and materials.
Romanticizing the early transmissions is cute and taps into nostalgia and the persistent idea that old things are better then new things... I dont see it that way. I appreciate old things for what they are and I understand the allure of simpler times gone by. I have lots of old things, Juke Boxes, old cars, pachinko machines, pinball machines etc. I have new stuff too, newer cars, hybrids, VR and modern game consoles. No comparison. It's for this reason my next race build is getting a turbo and a T56 Mangum which can be power up-shift'ed with an ignition cut. After that a DCT or electic.
Debating transmission synchro preference is like debating color preference or engine oil preference.....time uselessly spent.
My sole point was that the "early" synchros are not weak and most of the damage occurred after the first idiot worked on the clutch mechanical of hydraulic system.
Purely out of interest, have you ever owned a Porsche with the "early style" Porsche synchros?
10-12-2020, 09:42 PM
Dissapointed with the Spec Stage 2 clutch
