4L80 vss signal

[chris989]

Hello all,

Has anyone converted to an electronic trans (OD) from the original 350/400 turbo? If yes, what did you do about the VSS?

I am running a 4l80 with a MSD controller. The motor and the trans run fine but my idle has been erratically high. A guys at "gearheadEFI" said the original PCM needs the VSS for some reason to idle right.

If you made this swap, how did you hook up the original VSS to the 4l80?

Thanks,
Chris

[skyphix]

What engine are you running? What you're describing is something that happens in LS swaps but in that case, you just connect the VSS to the ECU/PCM. I am guessing you're running the older TBI setup?

What vehicle is it in?

Thanks

[chris989]

Originally Posted by skyphix

What engine are you running? What you're describing is something that happens in LS swaps but in that case, you just connect the VSS to the ECU/PCM. I am guessing you're running the older TBI setup?

What vehicle is it in?

Thanks

It is a v2500 burb, 5.7 TBI

[skyphix]

I believe that means the TH400 you had would have been one of the late TH400 which had a VSS. You may need to use a new DRAC or adapter box from jagsthatrun.com - if you already used your VSS to send to the MSD control box, you may have to use a splitter similar to what was used for the electronic gauges to split between the speedometer and the ECM.

If I was in your shoes, I'd be calling MSD since you're using an MSD controller rather than a newer PCM and harness which seems to be most common in this swap. That said, typically without VSS engines tend to idle low or die as you come to a stop rather than idle high. I'd be testing the IAC and TPS as part of my diagnosis.

[chris989]

Originally Posted by skyphix

I believe that means the TH400 you had would have been one of the late TH400 which had a VSS. You may need to use a new DRAC or adapter box from jagsthatrun.com - if you already used your VSS to send to the MSD control box, you may have to use a splitter similar to what was used for the electronic gauges to split between the speedometer and the ECM.

If I was in your shoes, I'd be calling MSD since you're using an MSD controller rather than a newer PCM and harness which seems to be most common in this swap. That said, typically without VSS engines tend to idle low or die as you come to a stop rather than idle high. I'd be testing the IAC and TPS as part of my diagnosis.

I called MSD after I made the post and was told the VSS signal from the 4l80 is the same as the 400T. He said i need to splice the OEM ECM to the same wires the MSD uses.

I hope it is that simple.

[skyphix]

Originally Posted by chris989

I called MSD after I made the post and was told the VSS signal from the 4l80 is the same as the 400T. He said i need to splice the OEM ECM to the same wires the MSD uses.

I hope it is that simple.

It would make sense since the 4L80E is simply the evolution of the TH400 and by the time the TH400 received a VSS the 4L80E was in development and starting to be put into trucks shortly thereafter. If you can simply tap the wire for the ECM signal then thats all the better!

[chris989]

I had time tonight to connect the OEM VSS wire and I can not find any connector or wire near the transmission without a home.

I have complete wire diagram book and it shows a connector with pink/blk, blk, brown blk being the ground, pink blk coming from the fuse box and brown being the signal.

I believe the vss gets its signal from the back of the speedo,, it has the little green box there and none of those wires exit the firewall.

Could the green vss box be bad???

thanks,
Chris

[Ryan Hubbard]

I have a 1990 V2500 Suburban that I installed a 4L80E in. You need to use the signal out of the transfer case and not the signal out of the back sensor of the transmission. The 4L80E 4x4 model does not have the wheel at the rear sensor to activate the VSS.

[chris989]

Originally Posted by Ryan Hubbard

I have a 1990 V2500 Suburban that I installed a 4L80E in. You need to use the signal out of the transfer case and not the signal out of the back sensor of the transmission. The 4L80E 4x4 model does not have the wheel at the rear sensor to activate the VSS.

I am running the MDS controller currently using the rear 4l80 sender, not the TF case. I never us 4wlo.

My 89 has the VSS in the dash but i am getting zero MPH reading at the ecm while data logging. I hope to make the OEM VSS work. just looking how to test it.

I have the 3 wire going from the EMC to the VSS, there are a few wires coming out the other side that i can not trace. also the is on single pin that is unhooked. Not sure what that is about?

[Ryan Hubbard]

Originally Posted by chris989

I am running the MDS controller currently using the rear 4l80 sender, not the TF case. I never us 4wlo.

My 89 has the VSS in the dash but i am getting zero MPH reading at the ecm while data logging. I hope to make the OEM VSS work. just looking how to test it.

I have the 3 wire going from the EMC to the VSS, there are a few wires coming out the other side that i can not trace. also the is on single pin that is unhooked. Not sure what that is about?

The problem with using the rear transmission sender is there is not wheel installed in the transmission case to activate the VSS and get a signal to the controller. The speedometer uses the output on the transfer case and that is the one you need to tie into. I tried using the rear of the transmission and found out that the 4x4 4L80E transmission does not use the rear output on the transmission. The pickup is on the passenger side of the transfer case.

Here is the sensor:

https://www.rockauto.com/en/moreinfo...301487&jsn=467

[chris989]

Originally Posted by Ryan Hubbard

The problem with using the rear transmission sender is there is not wheel installed in the transmission case to activate the VSS and get a signal to the controller. The speedometer uses the output on the transfer case and that is the one you need to tie into. I tried using the rear of the transmission and found out that the 4x4 4L80E transmission does not use the rear output on the transmission. The pickup is on the passenger side of the transfer case.

Here is the sensor:

https://www.rockauto.com/en/moreinfo...301487&jsn=467

The rear sender is working with the MSD controller. I am not having any issue there, I am trying to get the OEM VSS signal to my ECM because of a high inconsistent idle. The mechanical speedo is working. I have no idea how the cable driven speedo is hooked to the VSS, i guess i will take the dash apart tomorrow.

[Ryan Hubbard]

Originally Posted by chris989

The rear sender is working with the MSD controller. I am not having any issue there, I am trying to get the OEM VSS signal to my ECM because of a high inconsistent idle. The mechanical speedo is working. I have no idea how the cable driven speedo is hooked to the VSS, i guess i will take the dash apart tomorrow.

Then just tap into the same sensor as the one you are using for the MSD.

[chris989]

Originally Posted by Ryan Hubbard

Then just tap into the same sensor as the one you are using for the MSD.

I believe the TBI EDM needs to see 2ppm and the 4l80 is 16ppm.