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I`m currently working a swap project on my C20 1985 all parts are from a donor Cadi escalade 2007 6.2 6l80. going to mate an np208 to the 6l80 made my own adapter 2 the tc my concern is the VSS do i still need to feed the ECU with an aftermarket pulse converter or i can still depend on the internal VSS of the 6l80 especially when in 4lo.
I pull speed from OBDII via dakota digital device. It outputs tach, speed from the device, which is plugged in to OBDII port.
Not sure about how the computer knows if you are in 4WLO. I'm guessing if you use 4WD 2007 image for computer and have the right sensor on the transfer case to signal this, it'd work.
Do you really need speed output in 4W LO?
I believe so. That is what I am doing with my 6L80. I am getting the vehicle speed from the computer port of the E38 RCM to run the speedometer.
I not actually worried about the speed output but the ecu needs to know if the vehicle is moving and on what speed its running so the tranny can shift.
I pull speed from OBDII via dakota digital device. It outputs tach, speed from the device, which is plugged in to OBDII port.
Not sure about how the computer knows if you are in 4WLO. I'm guessing if you use 4WD 2007 image for computer and have the right sensor on the transfer case to signal this, it'd work.
Do you really need speed output in 4W LO?
I`m planning to upgrade my instrument with DD device but that`s happening when I get my truck running
so I still need the sensor output to the ecu and buy the pulse converter that delivers 4k/8k as an upgrade on da 208np
I not actually worried about the speed output but the ecu needs to know if the vehicle is moving and on what speed its running so the tranny can shift.
is your rig a 4x4 ?
No, not a 4x4. The E38 ecm gets the info from the data wires coming out of the 6L80 transmission control board that is internal on the 6L80. On the 4X4 with a transfer case I am not quite sure how that works.
What do the OEM 4x4 applications do, like the 4x4 tahoes, silverados, suburbans, escalades?
It should be obvious if you can take a look at the wiring schematics?
I'm guessing there is a 4WLO switch in the transmission indicating that gear? Or are they not manual transfer cases?
Also....the ECM calculates speed based on tire diameter and diff ratio it does not use a traditional VSS.
If you think about it, the ECM should still know when to shift, I'd think it 4WLO. Here is why: It would know the trans output shaft speed and the engine rpm (and throttle pedal position). What happens behind the trans shouldn't make a big difference. The 6L80 does shift quickly. In 4WLO first gear you'll get there quicker, but I don't think you'll over-rev before it shifts. Rev limiter wouldn't be disabled.
As an example, when I first got my truck and running, the wheel size was incredibly far off. The trans still shifted and I actually had no idea. Even after the programming change, I can't say it made a big difference in shift points.
What do the OEM 4x4 applications do, like the 4x4 tahoes, silverados, suburbans, escalades?
It should be obvious if you can take a look at the wiring schematics?
I'm guessing there is a 4WLO switch in the transmission indicating that gear? Or are they not manual transfer cases?
Also....the ECM calculates speed based on tire diameter and diff ratio it does not use a traditional VSS.
If you think about it, the ECM should still know when to shift, I'd think it 4WLO. Here is why: It would know the trans output shaft speed and the engine rpm (and throttle pedal position). What happens behind the trans shouldn't make a big difference. The 6L80 does shift quickly. In 4WLO first gear you'll get there quicker, but I don't think you'll over-rev before it shifts. Rev limiter wouldn't be disabled.
As an example, when I first got my truck and running, the wheel size was incredibly far off. The trans still shifted and I actually had no idea. Even after the programming change, I can't say it made a big difference in shift points.
Maybe I'm missing something?
Doug
Thanks for the input.
The 6l80 came with an awd transfer case there`s no 4lo signal switch i think i`ll have to reflash my ecu with a firmware that came with 4lo swtich i`m still not sure if i still need the 4lo signal if the engine`s ecu calculates and gets feeds directly from the drive shaft,engine rpm, peddle throttle, if it works ok that way and i really hope so i`d just reinstall back my speedo cable to the np208 nd move on with the project.
I would run it as is (with tune from AWD transfer case) and see how it works. I really don't think it will avoid shifting because you happen to be in 4WLO. And like you suggest, just use an old school speedo cable and that will adjust based on transfer case gear selection (HI OR LOW).
If you really want optimal control of the trans, you could install the BCM and do paddle shifters from the corvette tune.
I wanted to add a sport-mode tune to mine. But my tuner (cunningham motorsports in Temecula area) couldn't figure it out. He changed my shift points a bit, ran a bit more in pressure for positive shift feel and I think it is great. When I get on the gas, the trans adjusts to holding gears longer, downshifting sooner, etc. It more or less reads my mind based on throttle position settings.
worst case, you can always redo the tune later.
Doug
My half ton 4x4 Silverado 2013 vintage uses vss mounted on output shaft of t/c and a transfer case control module on the high speed buss to tell the TCM and ecu the rpm and if it's in low range. That's a puzzle I am currently working on solving for my landcruiser swap.
(I've heard the 6L80 shifts poorly in low range of the TCM doesn't get the message it's in low range) first off I've got to find a reasonable way to get a 40 pulse per rev (128k per mile) signal from the geared speedo cable output on the Toyota transfer case.
I hope to have more info soon.
I would run it as is (with tune from AWD transfer case) and see how it works. I really don't think it will avoid shifting because you happen to be in 4WLO. And like you suggest, just use an old school speedo cable and that will adjust based on transfer case gear selection (HI OR LOW).
If you really want optimal control of the trans, you could install the BCM and do paddle shifters from the corvette tune.
I wanted to add a sport-mode tune to mine. But my tuner (cunningham motorsports in Temecula area) couldn't figure it out. He changed my shift points a bit, ran a bit more in pressure for positive shift feel and I think it is great. When I get on the gas, the trans adjusts to holding gears longer, downshifting sooner, etc. It more or less reads my mind based on throttle position settings.
worst case, you can always redo the tune later.
Doug
I`m actually thinking about activating my paddle shifter with a vette tune but that`s when I'm 100% sure my tranny shifts smoothly w or wo the 40 pulse.
My half ton 4x4 Silverado 2013 vintage uses vss mounted on output shaft of t/c and a transfer case control module on the high speed buss to tell the TCM and ecu the rpm and if it's in low range. That's a puzzle I am currently working on solving for my landcruiser swap.
(I've heard the 6L80 shifts poorly in low range of the TCM doesn't get the message it's in low range) first off I've got to find a reasonable way to get a 40 pulse per rev (128k per mile) signal from the geared speedo cable output on the Toyota transfer case.
I hope to have more info soon.
so u swapped a 6l80 out of 2013 Silverado and you`re saying the 40 pulse is truly required for 4x4 swap gen IV, what tc you are bolting have u looked @ Dakota digital for the adapter.
I have double checked and confirmed that the VSS is not needed on the transfer case to the ecu everything works internally on the 6l80 so if anyone swapping a gen IV engine, tranny into a 4x4 rig VSS is a thing of a past
Thank u all for the inputs nd a big thanks goes to Brendan from lt1swap.
Everything I've found in this indicates the A6 doesn't shift well in lo range w/o the TCM knowing its in low.
And the Silverado definitely has one installed on the tail of the T/C that is wired to the TCCM which talks on the bus line.
I am using the chev cluster and want the warning lights off among other functions working so I am researching having a bus message simulator talk on the. Us telling the cluster and other modules that everything is present and working....I.E. ABS which I won't have......
Anyone get this figured out? i know gen4 trucks still used some manually shifted transfer cases so there should be a way to go around the TCCM and just send the 4Low signal to the ECM. Any ideas? thanks
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6l80 & a VSS ?? 
