DCT vs Automatic
Learn something everyday by driving and good Forum info!
Race Director
Joined: Nov 2012
Posts: 11,048
Likes: 3,390
Instructor
Joined: May 2019
Posts: 202
Likes: 75
You've obviously never owned a vehicle with the outstanding German-built ZF8. It is bullet-proof and universally praised. It is well-known the GM A8 was problematic, and DCT's have sucked on occasion as well.
The ZF8 is used by Alfa-Romeo, Audi, BMW, FCA, Jaguar/Land Rover, and Mercedes-Benz among others. They are infinitely tunable depending upon whether the manufacturer is going for sporty vs. sedate, and most have controls for changing the shift characteristics.
I've owned cars with ZF8s tuned such they are almost indistinguishable from the excellent PDK, and BMW among others have dumped DCTs in favor of the ZF8.
The ZF8 is used by Alfa-Romeo, Audi, BMW, FCA, Jaguar/Land Rover, and Mercedes-Benz among others. They are infinitely tunable depending upon whether the manufacturer is going for sporty vs. sedate, and most have controls for changing the shift characteristics.
I've owned cars with ZF8s tuned such they are almost indistinguishable from the excellent PDK, and BMW among others have dumped DCTs in favor of the ZF8.
Safety Car
Joined: Mar 2014
Posts: 4,482
Likes: 668
From: Kilmarnock Va
Understanding the difference between the Tremec DCT and a "slushbox" automatic will help explain some of the issues folks have expressed! It's NOT a "slushbox" (thank goodness or I'd be driving something else!) It does NOT have a fluid coupling torque converter that can provide smooth power from 0 speed and allow the car to creep forward say in stop-and-go traffic by modulating the brake pedal. Some have complained about the DCT NOT operating like their "slushbox!"
SIDEBAR
Think of the DCT as two standard shift transmissions (which it is. ) Each with it's own clutch. When you slow down, unlike a standard shift where you would disengage the clutch, the Tremec DCT 1st gear clutch does NOT disengage. It slips as some folks do with a standard shift when on an incline to keep it from rolling back (not good practice but can be done.) Not a problem with the C8 DCT as the clutch is bathed in transmission fluid that has a large liquid to liquid cooler. As the Chief Corvette Engineer said, it is not an excess wear issue, it's built to handle that slippage.
So as you slow down, at about ~3 mph the 1st gear clutch starts to slip, it has to so the engine doesn't stall. You can feel the slip (if you are preceptive.) So sure, you have to keep your foot on the brake or it will creep forward! Just as you must with a "slushbox" but the difference is with a "slushbox" there is no transition speed. The torque converter can transfer power smoothly from 0 mph.
Therefore in bumper-to-bumper traffic I would treat it more like a standard shift and let the car in front move a few car lengths then release the brake pedal so the clutch can fully engage and move forward. You can let it creep with the clutch slipping BUT you'll feel the difference. When I pull slowly into my garage, as the mirrors come close to the door edge, it does feel different than say the wife's BMW X5, which has a good "slushbox" (if that is possible.)
PS: Understand many folks are not gearheads and don't want to think thorough the mechanical differences but some of the "silent majority" who view Threads might appreciate this way of thinking about what's happening! Having only driven standard shifts for my DD in 60 years, getting used to the DCT was an issue. I drove in Manual Mode for a month AND when I came to a Stop Light pulled both shift paddles, which disengages BOTH clutches (the only way to disengage the clutches.) Then I released the downshift paddle when stopped and kept the upshift paddle depressed until ready to move forward. On a flat surface no need to keep my foot on the brake! BUT for the past 3 months drive a different way. I have Z MODE set with Power in Track, which provides a much more aggressive drive (as I was used to in my 2017 Grand Sport, etc.) I now am used to the slight slipping and don't bother with pulling both shift paddles to put them in neutral as I come to a stop. Most fun Vette of the 6 I have owned.
Just use the Tremec DCT to it's advantage and forget those old "don'ts" with DCT's as that is for older ones!
SIDEBAR
Think of the DCT as two standard shift transmissions (which it is. ) Each with it's own clutch. When you slow down, unlike a standard shift where you would disengage the clutch, the Tremec DCT 1st gear clutch does NOT disengage. It slips as some folks do with a standard shift when on an incline to keep it from rolling back (not good practice but can be done.) Not a problem with the C8 DCT as the clutch is bathed in transmission fluid that has a large liquid to liquid cooler. As the Chief Corvette Engineer said, it is not an excess wear issue, it's built to handle that slippage.
So as you slow down, at about ~3 mph the 1st gear clutch starts to slip, it has to so the engine doesn't stall. You can feel the slip (if you are preceptive.) So sure, you have to keep your foot on the brake or it will creep forward! Just as you must with a "slushbox" but the difference is with a "slushbox" there is no transition speed. The torque converter can transfer power smoothly from 0 mph.
Therefore in bumper-to-bumper traffic I would treat it more like a standard shift and let the car in front move a few car lengths then release the brake pedal so the clutch can fully engage and move forward. You can let it creep with the clutch slipping BUT you'll feel the difference. When I pull slowly into my garage, as the mirrors come close to the door edge, it does feel different than say the wife's BMW X5, which has a good "slushbox" (if that is possible.)
PS: Understand many folks are not gearheads and don't want to think thorough the mechanical differences but some of the "silent majority" who view Threads might appreciate this way of thinking about what's happening! Having only driven standard shifts for my DD in 60 years, getting used to the DCT was an issue. I drove in Manual Mode for a month AND when I came to a Stop Light pulled both shift paddles, which disengages BOTH clutches (the only way to disengage the clutches.) Then I released the downshift paddle when stopped and kept the upshift paddle depressed until ready to move forward. On a flat surface no need to keep my foot on the brake! BUT for the past 3 months drive a different way. I have Z MODE set with Power in Track, which provides a much more aggressive drive (as I was used to in my 2017 Grand Sport, etc.) I now am used to the slight slipping and don't bother with pulling both shift paddles to put them in neutral as I come to a stop. Most fun Vette of the 6 I have owned.
Just use the Tremec DCT to it's advantage and forget those old "don'ts" with DCT's as that is for older ones!
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,945
Likes: 12,359
From: NE South Carolina
^^^^
Yep for the ~75% of Vette owner's who drove "automatics" it is different. The "slushboxes," as I refer to them, all have a fluid coupling torque converter that can transmit power smoothly from 0 mph. And the wife has had some excellent "automatics" like her XJ Jag, CTS Caddy, followed by a Porsche Cayenne and her most recent two BMW X5 SUVs. Good "slushboxes' but no where near the Tremic DCT in performance and software options it provides.
And agree with the comment that the clutch slippage. which starts below ~3 mph, gets smoother with time. But as I pull into the garage and the driver's mirror tip gets 2 to max 3 inches from the wood door molding (my indicator that I have the needed clearance on the passenger side) I go very slowly. Feels much different than pulling into the garage with the wife's SUV! It's NOT like a "slushbox" automatic.
That said, IF you want to drive like a slushbox automatic, your option put it in Tour Mode and have at it! But if you're at all perceptive, when stopping at a red light or trying to creep forward in bumper to bumper traffic (like you can do with a "slushbox") it "feels" different.
For those who would like the "feel" a great performance transmission I suggest setting Z MODE with POWER set to TRACK. Can set all other controllable variables where you would like: Ride, eBoost, Steering and NPP. It's like driving a different car with very quick upshifts and most noticeable downshifts. It also never goes into V4 mode and will seldom shift past 5th or 6th. It will NOT downshift with modest throttle changes since you'll have plenty of torque in the lower gears. If just cruising on a section of road you can use the upshift paddle and go to higher OD gears. I drive it Z MODE 90% of the time.
Yep for the ~75% of Vette owner's who drove "automatics" it is different. The "slushboxes," as I refer to them, all have a fluid coupling torque converter that can transmit power smoothly from 0 mph. And the wife has had some excellent "automatics" like her XJ Jag, CTS Caddy, followed by a Porsche Cayenne and her most recent two BMW X5 SUVs. Good "slushboxes' but no where near the Tremic DCT in performance and software options it provides.
And agree with the comment that the clutch slippage. which starts below ~3 mph, gets smoother with time. But as I pull into the garage and the driver's mirror tip gets 2 to max 3 inches from the wood door molding (my indicator that I have the needed clearance on the passenger side) I go very slowly. Feels much different than pulling into the garage with the wife's SUV! It's NOT like a "slushbox" automatic.
That said, IF you want to drive like a slushbox automatic, your option put it in Tour Mode and have at it! But if you're at all perceptive, when stopping at a red light or trying to creep forward in bumper to bumper traffic (like you can do with a "slushbox") it "feels" different.
For those who would like the "feel" a great performance transmission I suggest setting Z MODE with POWER set to TRACK. Can set all other controllable variables where you would like: Ride, eBoost, Steering and NPP. It's like driving a different car with very quick upshifts and most noticeable downshifts. It also never goes into V4 mode and will seldom shift past 5th or 6th. It will NOT downshift with modest throttle changes since you'll have plenty of torque in the lower gears. If just cruising on a section of road you can use the upshift paddle and go to higher OD gears. I drive it Z MODE 90% of the time.
Last edited by JerryU; Dec 28, 2020 at 07:47 AM.
Melting Slicks
Joined: Apr 2013
Posts: 2,691
Likes: 140
I also treat it like a manual and wait for traffic to start moving and a gap form instead of inching forward in little bits.
