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With respect to holding power versus engagement range on the single disc clutches, I'm using a Spec Stage 2 (SP142). It's rated for 525 ft. lbs. and it hasn't slipped yet with my 1987 928's roughly ~550 ft lbs. Engagement range was initially short, but, as I broke it in, the range improved. The 928 transmission isn't perfect, but I'm very happy with mine on the whole. Zero shuddering, smooth and predictable engagement, no problems. And replacement of the single disc clutch is so easy that I won't be bothered much if it does wear out prematurely.
If you're switching to a dual disc, is there any reason not to use the older style timing wheel with a new ECU? They can handle the tooth count and if you'll need to tune the motor anyway, why not upgrade to a new ECU and save yourself time and money with the timing ring conversion?
why not upgrade to a new ECU and save yourself time and money
I'm not sure I'm understanding the rationale for switching to a dual disc setup- the stock GTS single disc clutch is fine for a stock GTS motor, unless you're planning on engine mods, a turbo, or supercharging in the future (?)
For a 5-speed conversion it seems like your options are:
2. Dual disc setup
-85-86 flywheel
-80-83 intermediate plate
-timing ring from an 87-95 automatic flywheel
-78-86 guide tube
- -06 release arm
- 80-86 pressure plate
-80-86 disc #1
-80-86 disc #2
-release bearing 78-86
3.A Spec clutch setup plus an S4 flywheel, etc.
4. One of Greg's Dual disc clutch setups.
Not sure what the cost/hassle quotient for each of these is, but I'd be talking to Greg about option #4, cost-wise it's going to be in the ballpark vs. the other options and it'll hold whatever power you might throw at it later.
Lol, there's overlap if you're also already doing major performance mods and need to retune the ECU. It is time and money ahead to install a new ECU versus buying a SharkTuner, buying the chips, buying a SuperMAF, buying an external WBO2 controller, buying a MAP sensor and gauge (if you're boosting it), etc. Let's not even talk about the SharkTuner headaches with logging or not being able to even look at the tune at all unless the car's ignition is turned on and you're plugged into the ECU.
If you have no tuning planned, and are just looking to change from single to twin disc, then changing the ECU for that makes no sense. For my $1k and a couple hours of my time, a Spec Stage 2 single disc clutch met my needs.
I upgraded () my '82 "rally" car to single disc.... and it works perfect as any other ( even modern) car !
I can speak out of experience , must have had sure +40 manual cars in my life. Never a auto.
Michael:
Your transmission arrived, yesterday. The pallet took some grief, but the ice chest and wrapping looks fine.
Wow that was incredibly fast! It was picked up on Tuesday. Thanks for the update Greg. Drop me an email when you have time to check it out and have some recommendations.
I need to re-read your notes on PSD vs LSD retrofit so I can answer your question on which way to go. Thanks again and I'm looking forward to hearing what you find.
Wow that was incredibly fast! It was picked up on Tuesday. Thanks for the update Greg. Drop me an email when you have time to check it out and have some recommendations.
I need to re-read your notes on PSD vs LSD retrofit so I can answer your question on which way to go. Thanks again and I'm looking forward to hearing what you find.
It's going to be a minute or two.....
I've got a GTS that needs to be on the track by February 15th, with two months of work that needs to be finished.
Kyle and I are here, by ourselves. Our helper/mechanic is off sick, again. (Missed 75 days, last year. Missed over 80 days the year before. Missed 65 days the year before that. Might be a trend?)
Not sure what you are going to do about the PSD.....suffer with the slow reaction time or convert it to a real limited slip, but I've developed the technology to be able to accomplish this and still have the internal oil pump work....
Hello friends, It's been a while since my last update. As a recap, the transmission is still being rebuilt and is making steady progress. I'll provide some details in that in a later post. But it would seem re-assembly is going to happen soon which is very exciting!
5 Speed Torque Tube
Meanwhile work has progressed on other fronts related to the conversion. For those who don't know, the Torque Tube Assemblies (TT) are different between automatic and manual transmission cars. The TT for the manual transmission cars is longer. I was lucky enough to source a compatible 5 speed TT assembly that was used but in really nice condition. The assembly included tired bearings, driveshaft, front shift rod, and insulating foam that was more or less crumbling to touch. The plan was to replace the TT internals.
Tear-down
Extracting the old bearings and drive shaft was a mid-evil exercise in brute force and heavy implements. I wish I had pictures for this step. The basic execution was to hammer out the shaft using a combination of blocks of wood to fit inside the tube, while at the same time setting up a stop against a wall to allow the staff to exit the other end (think long 2x4’s). Once I figured out the setup, it all went quickly and without damage to any of the components. The internals looked to be original and never to have been replaced. Curiously, there were three bearings and no balancer in this drive shaft. The existing drive shaft that was removed was in perfect condition all the splines were undamaged
Installing Bearings
New bearings and a drive shaft from @Constantine at Black Sea R&D. The parts included very detailed installation instructions that described supplies needed and insertion depths. I included a little video below of me inserting the bearings to the proper depth using the prescribed PVC tubing.
Installing Drive Shaft
Next up it came time to insert the driveshaft. Even though the instructions called for hammering with a block of wood, I didn’t feel comfortable with the potential impacts on the bearings so I rigged up this strap to pull the shaft to the exact correct position. It worked great.
All in all the everything went very smoothly, lots of steps, lots of special preparation, but all an all not complicated once I had comprehended the processes.
Foam Insulation
The foam insulation was fully intact but surface was crumbling and shedding badly. Handling was causing it to fall apart.
I decided to experiment with coating with rubber to help protect it and keep it intact. I read that spay on rubber coatings could melt the foam (probably from the solvents in the aerosol) so I tested using liquid rubber from Flex Seal. Testing showed no melting or damage so I have the exterior of the foam a couple coats and it turned out great, its now has a very durable exterior.
Amazingly enough, your transmission case/associated pieces has had all of the broken off fins completely repaired, is back from vapor blasting, has been tumbled, cleaned (2-3 times, at this point), and has been sealed with CeraCoat.
The simple part (assembling) willl occur this week!
BTW.....I'm completely out of flywheels for my absolutely incredible street/track clutches (again), but the people who machine my flywheels tell me that they will finish these in about 4 weeks. (Terrible supply chain issues, with metal and metal processing (heat treating, black oxide, etc.)
I'm having 10 flywheels made for the dual disc version (will hold 800 ft.lbs., is smoother than a stock single disc clutch, zero chatter, should last forever (from what we are seeing), and there are a few still unspoken for.]
This is, no excuses/no BS, the finest 928 clutch available.....by leaps and bounds!
Amazingly enough, your transmission case/associated pieces has had all of the broken off fins completely repaired, is back from vapor blasting, has been tumbled, cleaned (2-3 times, at this point), and has been sealed with CeraCoat. The simple part (assembling) willl occur this week!
This is fantastic news and as you can imagine I am super excited to begin! Thanks for the update Greg!
As Greg mentioned, he has repaired the transmission case. Sadly, several of the cooling fins were damaged and broken off as a result insufficient packaging when the transmission arrived to me from the original owner. Here are some photos of the transmission when I first received it. You can see at least 3 of the 7 fins that were broken. You can also see the metal strapping that was used to secure the transmission immediately understand why the fins broke. Additionally both metal straps had broken free from their mornings and the transmission was literally rolling around in the case. While none of this damage impacted the internal functionality of the transmission, you can imagine my disappointment when I cracked open the case.The seller felt pretty bad about the damage and we worked out an arrangement when he sent me the respective cross member.
And here are some photos that Greg sent me of the repairs he and his team made to the case. The repairs look like there was a lot of tedious work involved and the quality is outstanding. Special thanks to @GregBBRD for the attention to detail and extra effort.
Last edited by Michael Benno; 06-20-2022 at 01:51 PM.
01-14-2022, 02:11 PM
) my '82 "rally" car to single disc.... and it works perfect as any other ( even modern) car ! 
