No longer impossible! 996/997 transmission onto air cooled engines!

[TopTuning]

Product I've been working on for the last year will soon be available to all...

Swap kit for 996 / 997 six speed (NA) transmission onto air-cooled Porsche engines!

Completed on my test mule '75 911 using 996 transmission, I've put about 500 miles on the setup so far and driving it more every day.

What a huge upgrade it is! These transmissions are not only cheap and easily available, they shift amazingly well in all conditions. Shifting at 7000 rpm just takes a flick of the wrist! No more gentle, deliberate waiting for the older boxes to behave.

The stock gearing is absolutely a delight! The first few gears are nicely a little shorter, the 6th gear makes cruising on the freeway fantastic. Something like 2800 rpm at 80mph.

Plenty of different limited slip units and ratios are available for these boxes as well.


Even the reverse gear is synchronized and silent. Every gear is a breeze to select! Having both the 996 and 997 boxes opened up, they are build very well with wide, strong gears - similar to the beefy g56 style units I work on with the 959s.

I can't imagine ever breaking one of these with such a light weight chassis. And if you did, you can pick up one of these for about $2k all day long.


For the early chassis - this is not a job for the faint of heart! Requires completely cutting out the areas between lower control arm mounts, torsion bar tube etc. I already had coil overs and don't care at all about the useless backseats, so not a concern for me. The rear seat "hump" must be changed to 964/993 style "high hump"

I plan on making a rear seat delete / luggage dump to cover it all up nicely.

Linkage is cable which is fantastic. Numeric racing makes the cables and it's easy to adjust / extend the ends.

I'm also using the Numeric racing shifter unit, which has more adjustment and removes ANY slop in the system. The shifter is bolt action rifle feeling, while not transmitting any noise or vibration into the car.


The adapter system consists of a 1/2" 6061 aluminum plate CNC cut. This locates the transmission centering onto the air cooled engine.

A special flywheel / clutch / release bearing assembly makes everything work with factory 997 hydraulic release cylinder and arm.

The starter located by the adapter plate, and the mini starter is required. A special adapter for the starter allows perfect fitment and easy service.

Stock engine mounted oil cooler is a no-go. I've also developed a replacement plate for the stock cooler that allows AN fittings to your tank and cooler, using the stock in -engine thermostat.

Axles are easy! Your stock axles work with simply knocking out the locating pins and drilling out for bolts on the transmission side. This is only for the 94mm CVs. I may develop an upgraded, direct fit axle for the swap at a later time.

Brake lines and ebrake tubes need some massaging. Easy part of the job. This may not be as much of a factor when I finish the design for a CNC transmission mount. My current mount is plate stainless, welded together.

The shifter bracket is completely custom and relocated on the transmission. The forward / backward attachment point is moved to accommodate.



For the later, 964, 993 chassis this swap with be FAR easier, probably only really requiring room for the shift cables etc. Also a great unit to use with any other air-cooled flat six powered vehicle.

The adapter plate may also work with the newer 7 speeds, PDK, and some automatics, more research will be done here...


Lots of pictures and videos to come, this is an exciting upgrade that's really made me fall in love with the car all over again. I can't get enough of the driving experience now.

Feel free to ask any questions here or in my PM.

[TopTuning]

[Gonbad]

Timeline?

[TopTuning]

Originally Posted by Gonbad

Timeline?

Need to put some more miles on it before it's available, as I do with everything I offer!

Soon though ....

[eflight]

Originally Posted by TopTuning

For the early chassis - this is not a job for the faint of heart!

What do you consider early chassis?

[Gretz]

Sounds like everything before the 964, based on his initial post...

[TopTuning]

Originally Posted by Gretz

Sounds like everything before the 964, based on his initial post...

Correct

Not sure why pictures aren't working...

[porschyard]

What pedal assy are you using

Richard

[Matt Monson]

Who is making gears for them?

[shamrok]

Subscribed, love all the stuff you're doing for these cars. Keep it up!

[WonkoTheSane]

I've been curious about this being a possible thing for some time now. Awesome to see someone else actually making it happen. I loved the transmission in my 996, and wish my 915 could take the shifts my G96 could.

[LJ851]

Looking forward to seeing pictures of the modifications. Do you know the weight difference between an aluminum 915 and these gearboxes?

[tdw28210]

Subd. Pics please

[Classic 911]

Following


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[eastbay]

Congrats!

You are really on a roll with the new products lately, nice stuff.

[Turbo_pro]

Will your adapter plate support the Cayman transmission?
Obvious question, fitment in a 914/6.

[Trackrash]

Waiting to see what torsion bar tube mods need to be done.....

[Mr jamo]

Amazing! This is exactly what I was looking for

[safe]

Originally Posted by LJ851

Looking forward to seeing pictures of the modifications. Do you know the weight difference between an aluminum 915 and these gearboxes?

Double?
G96 175lbs (https://californiamotorsports.net/pages/porsche-996-c2-c4-transaxle-specifications)

[David Inc.]

Originally Posted by safe

Double?
G96 175lbs (https://californiamotorsports.net/pages/porsche-996-c2-c4-transaxle-specifications)

No way. I had a 996 at one point and dropped the transmission myself using jackstands in a parking lot. I'm not 175 pounds so I don't think the trans is either.