mark kibort

again, save your time and money , unless you get the gears closer together. for those of you that watch my videos, you can see shift points vs speed are near the same on the track vs the Zo6 .( i.e. same nmber of usable gears and spacing , with subtle difference in the final drive)

xschop

This is no internet myth and I've seen it personally, factory Dual Clutch Disc setup and all. The Piranha Brothers called bull****.

h011yw00d

Tell me you guys are talking about off-the-line speed 'cause my car already just about makes me soil my pants as it is. The concept of shifting into 6th at 130mph boggles the mind.

77tony

Dinsdale of The Piranha Bros showed up at the shop a few days ago, and yes, this 6 speed is real. T

IcemanG17

If I remember right, my old M3 (2008 E92) shifted into 6th at 150mph.....or was that 7th? I dunno.....all I know is my current 928 is about 70mph in 2nd, around 100mph 3rd and 120ish 4th....

Jon B.

It's relatively easy to come up with adapters to bolt the tube and transaxle on a stand. Fitting it in the car is a completely different ball game.

Most cars use sixth as another overdrive. Top speed is usually still archived in fifth.

Mike Simard

Is this installed in a car? Making the adapter is a tiny part of the work, having it fit into a 928 is another level of effort. A picture of an adapted trans sitting on the ground is not much more than a scribbled napkin.

I'm curious about this because I have a custom tranasaxle I'm about to install and can see some of the obstacles. Even simple things like axles and having the 5" TT fit can be trickier than you'd think. And then there's the elephant in the room of fitting the diff to the crossmember area envelope. I can't see that happening without major modifications or compromises.

Please post the results even if it doesn't go as planned, it could be very helpful to others.

GlenL

Besides "it's got six speeds" what are the needs for this?

If it doesn't handle more torque then it's a lot of work, and cost, for the minor benefit. I'd think people with cubic money are racing in GT3s.

xschop

I would like to see the MPG change with the T56. Not only that, it will be very interesting to see the Vette automatic grafted in.... TBF will be a non-issue with the Vette TT design.

Mike, I was going to graft the C5 rear differential to an AX-15 and stab it in my 948 and repro them until I figured out the machine time and various custom parts needed. It would have fit the 928 and the 944 with custom axles. After tearing apart a C5 differential, I realised it is a major design improvement because the bearing pre-load/backlash is set within the housing itself and R&P (differential change) is a matter of an hour or so without having to drop the entire trans....

Doug sent me a few more pics. The shifter location is just icing on the 6 speed cake....

Mike Simard

I hear you. My Jerico project involved making some large housings out of massive chunks of aluminum and then there were the precision splined parts, it's almost like making an entire transmission from scratch when at first you might think that it'll be a matter of just drilling a few adapter plates.

What's going on in that lower pic? I can't figure out the perspective, it looks like the trans is hanging down low and the crossmember cut in half or something.

Having the shifter be where the old one was is just too good!

xschop

Yeah, he said it's just an X-member mod away from being completed.

mark kibort

do some homework here.
2.2 gives you
1st 55mph
2nd 80mph
3rd 118mph
4th 155mph
and 5th ???? how much power do you have.

of course, if you are racing over 155mph, the 2.2 has a disadvantage, due to spacing, but below, with a flat HP curve, there is almost NO advantage of having closer gears. you need closer gears if you are dealing with a peaky HP engine, like that of a GT3, or turbo rice burner. if you can shift and stay in the peak HP range, post shift, closer gears are not going to mean much. however, with a peaky hp curve, close ratios get you back in the HP peak range.

dont confuse 6 or 7 speeds with close ratio. sometimes, as in the C5 vet box, the shift points are near identical to the S4 for real applications, like racing on a road course.

certainly, if you dont pick up strength, then again, what is the purpose?? what are you trying to do??

the 928 gear box is amazing for power up to about 400rwhp, and so is the stock clutch and rear LSD.

mk

xschop

Besides the Low RPM Hiway overdrive, an extra 60Lbs is added to the rear wheels and even beefier helicut gears are off the shelf as well as Dog gears for the not so Daily Driver friendly setups

1st gear 2.97:1
2nd gear 2.07:1
3rd gear 1.43:1
4th gear 1.00:1
5th gear 0.84:1
6th gear 0.56:1
reverse 3.38:1
Diff 3.42:1

My Spare C5 differential is 2.73:1 That opens yet another can of worms.

Comparo to old.......

G28.03 G28.05

3.601
2.4646
1.8194
1.3433
1.0
Rev 3.1621

Diff 2.75

Dinsdale Piranha

Are ya'll gonna sell this thing ? Looks like a c5 tranny lots of options. let me know what the price is!!!!!!!!!!!!

mark kibort

the vet 6th gear for example is 1.91 , so you can see that it allows for 250mph.
vet 5th is near the same ration as the 2.75 5th of the 928
4th of 3.42 is a little shorter than the stock S4 4th

3rd is pretty close to the S4 3rd.

2nd is , 1st is.

you see, its just not worth it, .

just give us the MPH in each gear at redline. then, you can compare.