Curiosity question about downshifting
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From: Ricerville
Curiosity question about downshifting All of this talk about the 6l80e has me thinking; Why is it OK to downshift manually a 6l80e but not necessarily good to downshift a 4LXXE? Is it because the computer can rev-match the engine on the 6l80? I'm just curious.
EDIT:
Or is it really OK to downshift a 6l80e manually? I assume that it is because they have the paddle shifters on the new Camaro and Corvette
EDIT:
Or is it really OK to downshift a 6l80e manually? I assume that it is because they have the paddle shifters on the new Camaro and Corvette
Launching!
Joined: Jan 2005
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From: Northern NJ
For all intent and purposes, the simple answer is that you CAN'T literally manually downshift a 6L80/90. It's all computer controlled to protect itself from overspeed downshifting. It's why all but the most savvy tuners are not able to eliminate the small 'delay' in up/downshifts. Four speed transmissions have their rooted designs in manual override controls, so those functions are still present in the latest electronic variants.
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From: Ricerville
I know it's computer controlled, but I have heard that downshifting a 4L60E is a great way to kill it quickly. Why is it ok to tell the computer to downshift/upshift a 6l80e, but not a 4l60e? Again, is it because the computer "protects" the 6l80/90e?
The 6l80e is a clutch to clutch trans (internally) so the driveline doesn't get shocked when it's manually downshifted. The rev match of the motor also allows this to happen smoother.
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From: Ricerville
I've heard there is a right way and a wrong way to do that. People say you need to "rev-match" when downshifting the 60e but the shop manual says to keep your foot off the throttle when downshifting. As for me, I just keep it in OD most of the time except when the computer can't make up it's mind whether to put the trans in 3rd or 4th. Then, if I'm at a stop, I will put it in D3. If I'm already moving in 4th, I'll get on the throttle to make it automatically downshift to D3, THEN pull the shifter back to 3. That sounds like the safest way downshift the 60e. Basically have it already in the gear you want to go into, then pull the shifter back. You're not manually downshifting it per se, but rather forcing an automatic downshift and then keeping it from upshifting and ticking you off.
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From: TN
Like TrueBlue said, a 6L80E downshifts and up shifts electronically, not manually.
It's manual shifter positions are P, R. N, D. No way to manually shift through it's 6 forward gears manually.
With some GM cars you have to move shifter to a TU/TD position that allows the trans to go to manual electronically control shifting.
Caddy 6L80E shifter with TU/TD manual shifting. Interfaces with trans via BCM (Body Control Module).
Pontiac G8 shifter, again with TU/TD manual shifting via BCM.
Corvettes with 6L80E do not go through a BCM and use a different shifting program than TU/TD shifted 6L's, that allows direct access to 6L's TCM allowing them to be electronically manual shifted via paddles anytime gear shifter is in Drive position.
The 6L80E in my 1966 car has been reprogrammed with Corvette program, and I use a G8 shifter that has been modified with two momentary contact switches that allow it to be TU/TD shifted once I shift it over in TU/TD position. CHeaper than adding Paddle shifter to do the same.
Any 4L65E or 4L80E can be electronically manually (ManualMatic) shifted too. Requires stand along TCU that is programed to do it. Here is link that explains how it's done.
It's manual shifter positions are P, R. N, D. No way to manually shift through it's 6 forward gears manually.
With some GM cars you have to move shifter to a TU/TD position that allows the trans to go to manual electronically control shifting.
Caddy 6L80E shifter with TU/TD manual shifting. Interfaces with trans via BCM (Body Control Module).
Pontiac G8 shifter, again with TU/TD manual shifting via BCM.
Corvettes with 6L80E do not go through a BCM and use a different shifting program than TU/TD shifted 6L's, that allows direct access to 6L's TCM allowing them to be electronically manual shifted via paddles anytime gear shifter is in Drive position.
The 6L80E in my 1966 car has been reprogrammed with Corvette program, and I use a G8 shifter that has been modified with two momentary contact switches that allow it to be TU/TD shifted once I shift it over in TU/TD position. CHeaper than adding Paddle shifter to do the same.
Any 4L65E or 4L80E can be electronically manually (ManualMatic) shifted too. Requires stand along TCU that is programed to do it. Here is link that explains how it's done.
What is Manumatic Shifting Technology?
Broken down to its simplest elements, Manumatic technology can be described as follows:
A computer program that allows an automatic transmission to emulate the shifting of a manual transmission.
In order for this manu-matic technology to exist and function, all of the following criteria must be met:
1) A COMPUTER.
2) Manumatic SOFTWARE loaded into the computer.
3) An ELECTRONICALY controlled transmission.
4) An ELECTRONICALLY controlled shifter.
So a TH350 (or TH400 or 700R4, or 2004R....) does not and cannot meet any of the above criteria. An LS1/4L60E with a factory computer comes close to meeting all of the criteria, but the computer does not contain manumatic software--nor is their any way to load the software into the factory computer, so an aftermarket transmission computer is still required. Bummer. Don't blame us--blame GM.
Now let's look at availability:
1) COMPUTERS: TCI, Powertrain Control Solutions, BigStuff3, Compushift.
2) MANUMATIC PROGRAMMING: Is loaded into all of the computers listed above.
3) ELECTRONIC Transmission: Actually the PCS controller will run virtually any electronic transmission. The other brands run 4L60E, 4L80E, AOD-E and 4R70W. The key here is that shifting and line pressure are controlled electronically.
4) ELECTRONIC Controlled Shifter: It bypasses the mechanical shifter and detent. Computers, programs and electronic transmission have been adapted to hot rods for years, the Shrifter is the first aftermarket electronic shifter that allows you to tap into the dormant shifting technology. All that we have built is a glorified switch. You could accomplish the the same function of our product with just a couple of momentary switches and coil cords. Likewise you can easily buy an electro-mechanical shifter from a junkyard. But neither alternative will install as cleanly or be as fun to drive as a paddle shifter.
The following link will take you to a detailed installation.
http://www.popularhotrodding.com/tech/0507phr_twst/
Broken down to its simplest elements, Manumatic technology can be described as follows:
A computer program that allows an automatic transmission to emulate the shifting of a manual transmission.
In order for this manu-matic technology to exist and function, all of the following criteria must be met:
1) A COMPUTER.
2) Manumatic SOFTWARE loaded into the computer.
3) An ELECTRONICALY controlled transmission.
4) An ELECTRONICALLY controlled shifter.
So a TH350 (or TH400 or 700R4, or 2004R....) does not and cannot meet any of the above criteria. An LS1/4L60E with a factory computer comes close to meeting all of the criteria, but the computer does not contain manumatic software--nor is their any way to load the software into the factory computer, so an aftermarket transmission computer is still required. Bummer. Don't blame us--blame GM.
Now let's look at availability:
1) COMPUTERS: TCI, Powertrain Control Solutions, BigStuff3, Compushift.
2) MANUMATIC PROGRAMMING: Is loaded into all of the computers listed above.
3) ELECTRONIC Transmission: Actually the PCS controller will run virtually any electronic transmission. The other brands run 4L60E, 4L80E, AOD-E and 4R70W. The key here is that shifting and line pressure are controlled electronically.
4) ELECTRONIC Controlled Shifter: It bypasses the mechanical shifter and detent. Computers, programs and electronic transmission have been adapted to hot rods for years, the Shrifter is the first aftermarket electronic shifter that allows you to tap into the dormant shifting technology. All that we have built is a glorified switch. You could accomplish the the same function of our product with just a couple of momentary switches and coil cords. Likewise you can easily buy an electro-mechanical shifter from a junkyard. But neither alternative will install as cleanly or be as fun to drive as a paddle shifter.
The following link will take you to a detailed installation.
http://www.popularhotrodding.com/tech/0507phr_twst/
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