Mike Simard

Here's a transaxle I'm about to fit to my car. Special thanks to Slateblue for the idea.
I've broken 2 928 transaxles this year and have no faith in them.
I've always dreamed of a real racing box with straight gears and dog lug shifting that can be shifted with enthusiasm and handle any power.
The criteria are:

*Fit into a 928 with no mods needed
*Use the stock 928 diff and wonderful 4 spider LSD unit
*Use Jerico type racing trans
*Use GM 12 bolt ring and pinions with no mods needed for ratio changes
*Use stock 928 axles and CV joints
*Larger TT shaft splines and clutch discs

The transaxle unit is now complete and I'm about to place it under the car and fit the TT and shift linkage, that's still alot of work.

Since my 928 TT splies were twisted, I assume they are going to be breaking so I'm using the slightly larger GM splines and making my own TT housing.

Here are some pics of the transaxle:

Mike Simard

Some random details:
I've hand radiused corners on the GM 12 bolt pinion gear, 3.08

Mike Simard

Here's the transaxle unit.
The GM ring gear is mounted to the 928 LSD unit. It's setup to use the early 8 disc LSDs and install with no adapter spacers needed.
Ring and pinion backlash setup uses shims at the outter bearing houses just like stock.
I'm leaving the ring gear out while I fit it in the car.

85euro928

OBehave

Mike you sir are my hero!
It is great to see the birth of ideas brought on by past experience and the will and desire to solve a problem only driven by the passion for the car and the skills of a man posessed!
Are you planning on this being a 4 spd only or are you going for more gears? I had always wondered when someone was going to try using the GM gear set as I always thought it as an option with adaptation.Seems like the shift linkage is going to be tricky or are you just going to electrical paddle shifting?
I am suscribed and can't wait to see more. If you need a test mule I have a car or two that could put one through it's paces.

Fabio421

...

Mike Simard

I know what you mean about 4 speeds seeming not as cool as 5 or 6. That used to be very important to me, when BMW came out with a 6 speed 850 it just seemed like the height of coolness to me.

Being in the racing community and having a W2W car changed all of that.
The 4 speed racing boxes like this are way beyond stock street boxes on the track. They are massivly strong, take serious floggin, can be shifted quickly even without the clutch at times and the parts for repair and ratio changes are readily available and not expensive.
I changed a ratio on mine and it was a call to Jerico, $250 and 2 days later I have a pair of gears that are a massive work of art.

I also found that I never used 5 gears. With an early box, 1st was useless and with a later 2.20 box 5th was.
The extra gears of a 5 or 6 speed need more space on the shaft which can weaken it and need to spin all the time which is parasitic drag.
Besides, Porsche used a 4 speed when the turbo 930 happened, there are real advantages with the simplicity.

BTW, thanks for the kind words, it really helps to be motivated when in the middle of a massive project!

Fabio, OMG, it's worth it do do something like this just to see what you'll post!

Lloyd

Mike, very impressive setup and looks to be a winner. I am discarding my 928 trans also, but not as complicated as your project. Only possible weak spot may be the stock axles. Check out www.swayaway.com for a solution for heavy duty Porsche axles.

U-928

wow

AirtekHVAC

Dang man....that is the sheet!

Dave928S

Shazam !!! ..... I'm impressed

I can imagine the amount of time and work to get it to this stage.

Leon Speed

This is sooo far over my head all I can say is "oooohhh, aaahhhh, shiney bits".

Dinsdale Piranha

WOW!!! I want one. How much??

Rob Edwards

Great, now I have to build a track car. Thanks, Mike......

Dave928S

Sounds like a good idea ... you must be running out of things to photograph ..