VETTE TRANNY INSTALLED-SOME TESTING RESULTS AT POST 157
05-17-2011, 11:59 PM
#167
Race Director
I got to see Larry's machine in person this weekend.... the attention to detail is VERY obvious....clearly lots of time and thinking went into this setup! Quite the opposite of my "Estate"...which is very much a gut and go type setup....
There is no doubts to the C5 transaxles better strength.....those can easily be made to handle 850+HP and have far more gear ratio choices.....I think Larry is running a 3.42....but I don't know what the actual 1-6 ratios are....granted not many applications really need a true 2.20 overall top gear, unless you are in ORR.... here is a ratio comparison I found...I don't know if Larrys is a M12 or MM6
Gear ratio comparisons of MM6 (base-model C5) vs. M12 (Z06):
Gear LS1/MM6 LS6/M12
1st Gear 2.66:1 2.97:1
2nd Gear 1.78:1 2.07:1
3rd Gear 1.30:1 1.43:1
4th Gear 1.00:1 1.00:1
5th Gear 0.74:1 0.84:1
6th Gear 0.50:1 0.56:1
Reverse 2.90:1 3.28:1
Axle Ratio varies 3.42:1
There is no doubts to the C5 transaxles better strength.....those can easily be made to handle 850+HP and have far more gear ratio choices.....I think Larry is running a 3.42....but I don't know what the actual 1-6 ratios are....granted not many applications really need a true 2.20 overall top gear, unless you are in ORR.... here is a ratio comparison I found...I don't know if Larrys is a M12 or MM6
Gear ratio comparisons of MM6 (base-model C5) vs. M12 (Z06):
Gear LS1/MM6 LS6/M12
1st Gear 2.66:1 2.97:1
2nd Gear 1.78:1 2.07:1
3rd Gear 1.30:1 1.43:1
4th Gear 1.00:1 1.00:1
5th Gear 0.74:1 0.84:1
6th Gear 0.50:1 0.56:1
Reverse 2.90:1 3.28:1
Axle Ratio varies 3.42:1
05-18-2011, 12:25 AM
#169
Administrator - "Tyson"
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TREMEC:
http://www.ttcautomotive.com/english/products/t-56.asp
"This six-speed overdrive transmission was developed for adaptation to a wide range of vehicle requirements. Currently, the TREMEC T-56 is being used on the Dodge Viper, Chevy Corvette Z06, Ford SVT Mustang Cobra, Aston Martin DB7 Vantage and V12 Vanquish, and Holden Commodore and Monaro."
If it makes you guys feel better, tell everyone you have the Aston Martin V12 Vanquish transmission in your 928
http://www.ttcautomotive.com/english/products/t-56.asp
"This six-speed overdrive transmission was developed for adaptation to a wide range of vehicle requirements. Currently, the TREMEC T-56 is being used on the Dodge Viper, Chevy Corvette Z06, Ford SVT Mustang Cobra, Aston Martin DB7 Vantage and V12 Vanquish, and Holden Commodore and Monaro."
If it makes you guys feel better, tell everyone you have the Aston Martin V12 Vanquish transmission in your 928
05-18-2011, 09:09 AM
#170
My C5 differential (2.73) has a Getrag stamp on it. What's unique about the C5 diffs is that you can remove and install the diffs for different ratios without the hassle of resetting R&P backlash as the preload is done on the back side cover with a self contained shim system.
05-18-2011, 09:24 AM
#171
Drifting
Awesome post; you took the words right out of my mouth. The 928's design, basic chassis, and suspension are enough to make me love the car. A 928 engine is prefereable, but with the cost to maintain and/or build one for serious track use really makes it difficult. Changing the transmission for something better really doesn't affect the "928-ness" at all IMO, if done correctly.
Larry-
Great job man. I can't believe how quickly you got this done and look forward to more updates/impressions.
Larry-
Great job man. I can't believe how quickly you got this done and look forward to more updates/impressions.
05-18-2011, 09:41 AM
#173
Drifting
Any car is more than the sum of it's parts.
Lotus has historically made some of the best chassis in history from Indy, to F1 and the latest Elise. They've held almost every brand engine from Ford, Chevy, Cosworth, and now Toyota. God knows how many different transmissions.
They are all considered a Lotus. McLaren holds the same kind of history as goes Lola and a countless number of cars over the last century.
It's not our fault Porsche decided to go their arrogant ways with the 5-speed and designed their own versus buying a much stronger "off the shelf" unit back in 1978. Nobody has a problem with the Mercedes transmission in the auto's.....
Point is, what if Porsche had installed a "T-5" or some other generic 5-speed into the 928 and we were simply upgrading to a newer version, would the same question apply?
This is not a "Corvette" transmission, it's not made by GM. It just happens to be the same unit Chevrolet puts in their sports car
Lotus has historically made some of the best chassis in history from Indy, to F1 and the latest Elise. They've held almost every brand engine from Ford, Chevy, Cosworth, and now Toyota. God knows how many different transmissions.
They are all considered a Lotus. McLaren holds the same kind of history as goes Lola and a countless number of cars over the last century.
It's not our fault Porsche decided to go their arrogant ways with the 5-speed and designed their own versus buying a much stronger "off the shelf" unit back in 1978. Nobody has a problem with the Mercedes transmission in the auto's.....
Point is, what if Porsche had installed a "T-5" or some other generic 5-speed into the 928 and we were simply upgrading to a newer version, would the same question apply?
This is not a "Corvette" transmission, it's not made by GM. It just happens to be the same unit Chevrolet puts in their sports car
My post was not to put down the hard work that went into this incredible conversion.
I look forward to more results and some pictures.
Brad
05-19-2011, 11:38 PM
#174
Rennlist Member
Thread Starter
Thanks for the kind words regarding the conversion. Sorry to take so long getting back to it, but been busy figuring out what to do next.
A few answers to questions posted:
CONTROL ARMS AND CAMBER: After looking at tire wear and temps with 2 neg, decided to build upper control arms that would allow for more. The inside fronts weren’t wearing nearly enough. At 3.25 neg, still not getting enough inside wear, but will probably stay at 3.25-3.5, for now. Also, we’ll be lowering front pressures in order to get more tire roll to outside. Rears are 1 neg. Using shaved RA1s. Front 1,000lb shocks have wheel rate about 600 lbs. Penske’s set fairly light on bump and rebound. Upper control arms are solid mounted (rod ends) and the lowers are bushed with Delrin. Also, repositioned lower shock mount location and plan to move it outward, now that we know how much clearance we have.
PADS vs SPEED: We had c5 single piston (1.25” sweep) with worn street pads on the rear. No proportioning valve and no ABS. The fronts were 50-60% Pagid 19s on GTS calipers and cryo’d solid GTS rotors. Shifting into 5th at 6,600 (end of pit wall), running out a bit more, so probably hitting 155 or so before braking pretty hard to limit corner speed. Came in with lots of odor and smoke off the pads, so we put new 19s on and took it a lot easier the rest of the sessions.
TIMES: We set out to run 2:04-2:05, which was fast enough to test the suspension and slow enough that I could concentrate on what was happening to the car. Fastest bypass lap was 2:01.7 in the last session Sat and 2:03.5 over the top (w/ 2 wheels off) on Friday.
PICTURES: For what should be obvious reasons, we're not posting any pictures until we have a kit on the shelf and ready to sell (fully tested and refined).
RATIOS: 2.66, 1.73, 1.35, 1.00, .74, .50 with 3.42 diff.
PSD: The PSD was unpredictable on the track, especially on really tight turns. We confirmed it was working. It will be for sale, along with 82 and 87 open diff 5 speeds, several 8 disc LSDs, three rebuilt 4 speed autos, several motors, exhausts, interiors and a ton of other parts we accumulated with the 91GT, 89S4, 86.5 and 82. Can’t take the time to price everything out, but if someone needs something specific that you re pretty sure we have, PM me. Most of the stuff we have we paid premium prices for, so expect same if we sell. Some of the stuff we got cheap and will sell cheap.
NEXT: We will be converting my car to a lighter clutch, a stronger transmission/diff/axle set up and bigger brakes in about 6 weeks, once the parts arrive. In the meantime, we will be having axles made to join the c5 diff to stock 928 uprights/hubs. Hopefully, the first kit developed will allow the use of the c5/c6 transaxle without modification to the chassis (other than welding mounting brackets). We also have to figure out exhaust routing conflicts that may or may not exist with the various combinations of 928 and diffs that might be possible. It would help if all of you would be in favor of straight pipe headers out the hood.
A few answers to questions posted:
CONTROL ARMS AND CAMBER: After looking at tire wear and temps with 2 neg, decided to build upper control arms that would allow for more. The inside fronts weren’t wearing nearly enough. At 3.25 neg, still not getting enough inside wear, but will probably stay at 3.25-3.5, for now. Also, we’ll be lowering front pressures in order to get more tire roll to outside. Rears are 1 neg. Using shaved RA1s. Front 1,000lb shocks have wheel rate about 600 lbs. Penske’s set fairly light on bump and rebound. Upper control arms are solid mounted (rod ends) and the lowers are bushed with Delrin. Also, repositioned lower shock mount location and plan to move it outward, now that we know how much clearance we have.
PADS vs SPEED: We had c5 single piston (1.25” sweep) with worn street pads on the rear. No proportioning valve and no ABS. The fronts were 50-60% Pagid 19s on GTS calipers and cryo’d solid GTS rotors. Shifting into 5th at 6,600 (end of pit wall), running out a bit more, so probably hitting 155 or so before braking pretty hard to limit corner speed. Came in with lots of odor and smoke off the pads, so we put new 19s on and took it a lot easier the rest of the sessions.
TIMES: We set out to run 2:04-2:05, which was fast enough to test the suspension and slow enough that I could concentrate on what was happening to the car. Fastest bypass lap was 2:01.7 in the last session Sat and 2:03.5 over the top (w/ 2 wheels off) on Friday.
PICTURES: For what should be obvious reasons, we're not posting any pictures until we have a kit on the shelf and ready to sell (fully tested and refined).
RATIOS: 2.66, 1.73, 1.35, 1.00, .74, .50 with 3.42 diff.
PSD: The PSD was unpredictable on the track, especially on really tight turns. We confirmed it was working. It will be for sale, along with 82 and 87 open diff 5 speeds, several 8 disc LSDs, three rebuilt 4 speed autos, several motors, exhausts, interiors and a ton of other parts we accumulated with the 91GT, 89S4, 86.5 and 82. Can’t take the time to price everything out, but if someone needs something specific that you re pretty sure we have, PM me. Most of the stuff we have we paid premium prices for, so expect same if we sell. Some of the stuff we got cheap and will sell cheap.
NEXT: We will be converting my car to a lighter clutch, a stronger transmission/diff/axle set up and bigger brakes in about 6 weeks, once the parts arrive. In the meantime, we will be having axles made to join the c5 diff to stock 928 uprights/hubs. Hopefully, the first kit developed will allow the use of the c5/c6 transaxle without modification to the chassis (other than welding mounting brackets). We also have to figure out exhaust routing conflicts that may or may not exist with the various combinations of 928 and diffs that might be possible. It would help if all of you would be in favor of straight pipe headers out the hood.
05-20-2011, 01:30 PM
#176
Rennlist Member
Thread Starter
The G28.55 PSD tranny and TT have been sold to Rob Edwards in SoCal. We need to find someone to transport it down to Anaheim from NorCal. I plan to take it from Carson City to Infineon on June 11-12 and hopefully someone can pick it up there and hold it for future delivery or deliver it themselves to Rob. With any luck, there will be a SoCal racer at the track with room in or on their trailer.
05-20-2011, 02:04 PM
#178
Not the sharpest tool in the shed
Rennlist Member
Rennlist Member
The G28.55 PSD tranny and TT have been sold to Rob Edwards in SoCal. We need to find someone to transport it down to Anaheim from NorCal. I plan to take it from Carson City to Infineon on June 11-12 and hopefully someone can pick it up there and hold it for future delivery or deliver it themselves to Rob. With any luck, there will be a SoCal racer at the track with room in or on their trailer.
05-20-2011, 02:07 PM
#179
Archive Gatekeeper
Rennlist Member
Rennlist Member
Dan, thanks for the offer- if I don't find a transport solution before that I'll take you up on the offer . Neither Larry nor I are in any great rush.
. Neither Larry nor I are in any great rush.
05-21-2011, 01:49 AM
#180
Nordschleife Master
Im gonna be looking for rebuildable G28.55 or 57 in between 3 and 6 months.
Are you ever in LA with your 928 MONSTER? If so you need to stop by work sometime and let me take you out in some new Porsche metal.