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Thread: Dual Clutch Transmission (DCT)
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06-09-2020 #1Registered User
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- Jun 2020
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Dual Clutch Transmission (DCT)
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.
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06-09-2020 #2Registered User- Join Date
- Jun 2020
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- 36
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>
06-10-2020 #3