2007.5 Silverado th400 swap VSS help

[RJSenterprise]

2008 Silverado, working on buttoning up a TH400 swap and trying to get the speedo working again. I have the 4L60e range sensor plugged in and in Neutral so I can start the truck. I took both VSS wires and connected those to the Wheel speed sensor but I still couldn't get it to work. Is there something else that I didn't do in the tune? I disabled all ISS and OSS, enabled Wheel speed output and still didn't work. I purchased the dakota digital GPS-50 but i wanted to give the free way one last shot before I install lol.

[Shrek]

This topic has been beaten to death over the years. Plenty of threads discussing why the HPT Scanner constantly displays "158 MPH".

The Gen 4 platform that you are working with would have originally had an ECM and a TCM - in your case an E38 and a T42.

Your E38 ECM is programmed to receive speed data over the CanBus network, as it was originally paired with a TCM.
Your E38 ECM will not recognize speed data from a pulsed source - not from the wheel speed sensor, and not from the Dakota Digital GPS box.

Your E38 ECM needs to be programmed with a manual transmission calibration - to interpret pulsed speed data. In a Hotrod / conversion vehicle this is no problem. In your OEM Silverado this will be no easy task - as no OEM Silverado manual transmission calibration exists.

[RJSenterprise]

This topic has been beaten to death over the years. Plenty of threads discussing why the HPT Scanner constantly displays "158 MPH".

The Gen 4 platform that you are working with would have originally had an ECM and a TCM - in your case an E38 and a T42.

Your E38 ECM is programmed to receive speed data over the CanBus network, as it was originally paired with a TCM.
Your E38 ECM will not recognize speed data from a pulsed source - not from the wheel speed sensor, and not from the Dakota Digital GPS box.

Your E38 ECM needs to be programmed with a manual transmission calibration - to interpret pulsed speed data. In a Hotrod / conversion vehicle this is no problem. In your OEM Silverado this will be no easy task - as no OEM Silverado manual transmission calibration exists.

I did a search in a lot of forums but no one seems to have an answer of getting it to work. My Speedo reads zero all the time, same in the scanner. So whats the exact path of how it originally got the speed information? I couldn?t find a wiring diagram online. I did not remove the TCM at all.

[blindsquirrel]

If you still have an auto trans ECM OS and left the original TCM in place the VSS has to be wired to the TCM as it was with the original trans. From there the TCM sends the VSS data to the ECM over CAN.

screenshot.04-12-2021 08.26.34.png screenshot.04-12-2021 08.26.36.png

[RJSenterprise]

If you still have an auto trans ECM OS and left the original TCM in place the VSS has to be wired to the TCM as it was with the original trans. From there the TCM sends the VSS data to the ECM over CAN.

screenshot.04-12-2021 08.26.34.png screenshot.04-12-2021 08.26.36.png

So basically the VSS plug that went into the tail shaft, I can hook it up to a Dakota digital GPS for speed?

[Shrek]

I did a search in a lot of forums but no one seems to have an answer of getting it to work. My Speedo reads zero all the time, same in the scanner. So whats the exact path of how it originally got the speed information? I couldn?t find a wiring diagram online. I did not remove the TCM at all.

OK - a couple of things.

In the HPT Scanner, your displayed speed will be zero - as long as the TCM is on the communications line. If you do away with the TCM, the displayed speed would be 158 MPH.

The solution to this issue has been posted many times - you have two options.

Option #1:
As Blindsquirrel highlighted in post #4.
Keep the TCM in use, and on the communications line. Provide the TCM with a pulsed speed signal - which is what it is expecting.

Option #2:
Remove the TCM and all associated wiring.
Reprogram the ECM with a manual transmission calibration. Provide the ECM with a pulsed speed signal - which is what it is now expecting.

[RJSenterprise]

OK - a couple of things.

In the HPT Scanner, your displayed speed will be zero - as long as the TCM is on the communications line. If you do away with the TCM, the displayed speed would be 158 MPH.

The solution to this issue has been posted many times - you have two options.

Option #1:
As Blindsquirrel highlighted in post #4.
Keep the TCM in use, and on the communications line. Provide the TCM with a pulsed speed signal - which is what it is expecting.

Option #2:
Remove the TCM and all associated wiring.
Reprogram the ECM with a manual transmission calibration. Provide the ECM with a pulsed speed signal - which is what it is now expecting.

Ill keep the tcm, what settings do I need to put in hptuners if I use the wheel speed sensor tied into the VSS plug that originally went to the 4l60e?

[RJSenterprise]

Figured I would update this thread since no one really helped or knew what to do and every SINGLE post I came across during search ended up at a dead end! I did a trans swap on a 2007.5 NNBS. Originally a 4l60e, now a th400. I left the range sensor plugged in and in neutral so the truck would start. All other sensors zip tied. Tried to use the wheel speed sensor wired to the VSS with no luck. Purchased the Dakota digital GPS speedo and I can confirm that it works! Only utilizing one wire going to the original VSS wiring. It is a bit spotty in some areas.

Used the 8000 ppm setting, turned off ISS in the tune, modified the calibration until it all matched, wheel speed, true speed and speedometer.

[eXo3901]

Three separate posts saying what needed to be done.