Dual Clutch Transmission (DCT)

[DblTrbl]

First of all, I don't know if this post belongs in the manual or automatic transmission section or both.

I did a bad thing a little while ago. I was hanging out with my friends at Maximum PSI, a BMW performance shop where it's not uncommon for them to work on 1000HP + BMWs.

They were schooling me on DCTs and showed me a video of an F80 M3 running through the gears of the DCT transmission and I had an epiphany. I'll link a video and you'll see why.

I want a DCT in my turbo LS C3 vette!!! Don't get me wrong, I love my 4l80E. But the Getrag DCT are 7 speed, electronic, dual wet clutch transmissions with almost instantaneous shifting. Some are set up with a clutch control pedal for aggressive launches while some don't need it. Shifting can be slow and soft for cruising or quick and aggressive for racing.

DCTs can be found in the C8, Mclaren, Ford GT, Ferrari and so on.

Gettrag stock clutch DCTs can handle 600 ft/lbs of torque and with upgraded clutches or higher line pressures, way, way over that. Other than clutch wear, they just don't break. The majority of the internals are like two manuals transmissions, each connected to their own multi disk wet clutch and controlled electronically by the internal computer brain and/or linked electronically to a clutch pedal with a potentiometer instead of hydraulic fluid (You can think of this as a DBW clutch pedal).

One of the internal manual gearboxes is for the odd gears and the other is for the even gears. So lets say you're on an odd gear, the next even gear can be synchro-meshed ahead of time so when you need the next shift, one clutch disengages while the other engages and the shift is instantaneous.

There are two gear ratio versions.
The gear ratios: compared to my 4l80E

-----Gettrag DCTs-------------4L80E
1st - 4.806------ 4.78-------- 2.48
2nd - 2.59 ------ 2.933--------1.48
3rd - 1.701-------2.153--------1
4th - 1.277-------1.678------- 0 .75
5th - 1 -----------1.39
6th - 0.844-------1.203
7th - 0.671 -------1.0

The Getrag unit has a parking pawl with an external linkage. Some folks permanently lock it out, some hook up some cable system or motor to operate it.


So the problem is that BMW DCTs have an internal computer that controls the trans. And the protocol to the transmission is highly encrypted and are VIN locked to the engine. When an M3 crashes, the transmission cannot be installed in another car. It's pretty useless and therefore readily available and reasonable. No one has broken the encryption yet to my knowledge, although I've heard some buzz about it.

There are already some standalone computer brains available to control these and some others in development. These replace the locked internal computers and some have to be manually wired in. I'm thinking of either using one of these or designing my own.


At a minimum, here's some stuff that will have to be done.
-An adapter plate to mount the Gettrag to the LS.
-Some connection between the DCT input shaft and the LS flywheel.
-Fitting the starter.
-Output of the trans goes to a 3 bolt plate connected to a rubber driveshaft isolater (guibo) so an adapter from that to driveshaft (1350 in my case).
-Probably have to modify or replace the trans mount, but the one in my Vette bolts in, so maybe not too hard.
-Buy a replacement computer/controller or make my own. Cut the old computer out and wire in the new one.
-Change my DIY 4l80e controller from 4speed w/lockup to 7 speeds and connect to the new computer.
-I already have a parking brake so that's not a problem.
-Adapt the oil cooler lines to the Gettrag. There are kits with adapters to AN fittings.
-Maybe change the rear end rear ratio.
-Change the shifter to a sequential style or just delete it or optional paddle shifters
-Maybe a new length driveshaft.

[DblTrbl]

This is one of the videos that got me interested. First part of the video they have a conventional clutch. Then they swapped in a BMW DCT.


http://.<a href="https://www.youtube...hCvE&t=30s</a>

[John McIntire]

I'm interested in this too.

YouTube link is broken...

[raustinss]

Attention has been gotten lol

[DblTrbl]

I'm new to the forum so excuse the learning curve.

Let's try the video this way.

https://youtu.be/QcJL43NhCvE

[DblTrbl]

I bought the BMW V8 version of the DCT. I think it will be a better fit for the starter. The final gear is 1:1 on the V8 version, so a rear end gear ratio change is in my future.

[DblTrbl]

Ordered this from domieng






They also have an adapter that has an AN fittings for the oil cooler lines.

[DblTrbl]

Started some work on the Dual Clutch Transmission.



There are two oil pans. One on the bottom and one one the side. The side one is the access to the computer and valve body.

[DblTrbl]

There is no torque converter or external clutch. The transmission spline connect directly to the engine flex plate or starter ring.





Here's the DCT next to the 4L80E for a rough size comparison.

[DblTrbl]

Started dissecting the Getrag V8 DCT.



FYI, I have a transmission work table which originally started it's life as a computer rack. There is a hole in the center of the top so all the fluid that spills out goes down the hole into a bucket below.

The connector goes up and leaves the top of the transmission. The cover appears to be resealable.

The first thing is the computer. Below that is the valve body which has 10 solenoids.

[DblTrbl]

The back side of the valve body has hydraulic actuators that effectively do the shifting just like you would with a manual transmission shifter, but the fluid for these actuators is controlled by the solenoids.



The actuators in the valve body move the levers that link to the synchros.


The internals are pretty much like most manual transmissions with the syncros and all that except.... There are two sets of gears. One set if for the even gears and the other set is for the odd gears.

There are sensors that let the trans know the position of the gear shift levers and some other sensors I haven't figured out yet.

[DblTrbl]

stevieturbo on the LS forums always finds great info and found his link with lots of additional info.

https://www.seemslegitgarage.com/pos...R7_ITfRR12UFDQ

[John McIntire]

Wow! That is cool! Looks very compact!

[John McIntire]

So it looks like there's an inline 6 and a V8 version, the only difference being the bellhousing bolt pattern, and then 2 versions of each, one with a 1:1 final drive and the other with a double OD?

What have you found as far as controllers?

[DblTrbl]

So it looks like there's an inline 6 and a V8 version, the only difference being the bellhousing bolt pattern, and then 2 versions of each, one with a 1:1 final drive and the other with a double OD?

What have you found as far as controllers?

Two main ones I've heard used are https://www.dkgecu.com/cars/ and http://htg-tuning.com/.

I've seen the DKG one actually running.

[andrewb70]

Great thread. Carl, the images are loading fine.

Andrew

[andrewb70]

Carl,

Have you been in touch with any of the ECU controller vendors, like DKG? I don't see pricing on their website.

Andrew

[DblTrbl]

Carl,

Have you been in touch with any of the ECU controller vendors, like DKG? I don't see pricing on their website.

Andrew

I've been in touch with them. They are working on getting their Version 3 unit out. I don't have pricing.

[loudandproud]

Just ordered my Domiworks kit today. I will be following your progress closely! Good stuff man.

[andrewb70]

Just ordered my Domiworks kit today. I will be following your progress closely! Good stuff man.

You and Carl are at the pointy end of the spear for this trans being used with LS engines.