VSS issue in 6.0 swap in 94 4x4

[HPICamaroSS]

Speedo wire should come from the PCM. The VSS wires go to the PCM and the PCM processes that info and sends the signal directly to the speedo on another wire. Should be a dark green/white wire from pin 50 of C-2 connector(Red or Green,depending on year).

Thanks! thats a very good tip right there, exactly what I was looking for! So on the transfercase what are the 2 sensors? I am pretty sure the very rear one is the vss whats the one before that. Do I do anything with that first sensor on the tcase?

[slow94]

The first sensor/switch on your transfer case is used to engage the 4wd actuator in your front axle, it also illuminates your floor shifter, and signals the pcm when you have shifted to 4lo, it also has some function for 4wal/rwal.

[HPICamaroSS]

The first sensor/switch on your transfer case is used to engage the 4wd actuator in your front axle, it also illuminates your floor shifter, and signals the pcm when you have shifted to 4lo, it also has some function for 4wal/rwal.

So I just leave that first sensor alone? Dont do anything with it?

[slow94]

Just to make sure we're talking about the same thing, its the sensor in the middle of this picture? If so, it has a seperate harness and will need to be hooked up or you will not have 4wd. This wire engages your front axle actuator. By shifting the transfer case your engaging the driveshaft, but it will only free spin.

[HPICamaroSS]

Just to make sure we're talking about the same thing, its the sensor in the middle of this picture? If so, it has a seperate harness and will need to be hooked up or you will not have 4wd. This wire engages your front axle actuator. By shifting the transfer case your engaging the driveshaft, but it will only free spin.

I am pretty sure that is it. It looks a tid bit different. My vss looks like its on the tail shaft of the tcase. Then the 4wd actuator plug ( or whatever you want to call it) is in the middle. I think we are on the right track. So keep the middle plug the way it is. Dont touch it, dont splice into it etcc.....?

[slow94]

All of this is assuming your still running the 94 ifs and np241 that came in the 94 originally

[Mickeymotormount]

Looks like mine on my '93. The tailshaft sensor is the VSS that goes to the PCM. As depicted above, that sensor shown goes to the floor shift lever.

I left everything original except for hooking up the 4wd Low wire from the PCM. That is something that needs to be done. Since the drivetrain will be spinning at a much slower RPM compared to engine speed in the 4 Low position, the 4 low wire from the PCM must be grounded so the PCM "knows" the drivetrain is in 4 low and shifts the trans accordingly. I mistakenly removed that from my modified original harness and now must repin the PCM and find how I can get the wire grounded in the 4 Low position. It will take some doing but I figured I'd mention it so someone else doesn't make the same mistake I did.

[HPICamaroSS]

Looks like mine on my '93. The tailshaft sensor is the VSS that goes to the PCM. As depicted above, that sensor shown goes to the floor shift lever.

I left everything original except for hooking up the 4wd Low wire from the PCM. That is something that needs to be done. Since the drivetrain will be spinning at a much slower RPM compared to engine speed in the 4 Low position, the 4 low wire from the PCM must be grounded so the PCM "knows" the drivetrain is in 4 low and shifts the trans accordingly. I mistakenly removed that from my modified original harness and now must repin the PCM and find how I can get the wire grounded in the 4 Low position. It will take some doing but I figured I'd mention it so someone else doesn't make the same mistake I did.

Thats really good info. I was having the same problem. Is there any wire specifics you can give me. Routing/ Splicing into what wire? Color of wires? Thanks!

[HPICamaroSS]

AND since my 94 tcase has a different style vss connector compared to nelsons new style vss pigtail, is that all you do is cut off their pigtail and put the old OBS connector on their harness so it plugs into the tcase? Does it matter what way the wires go?

[Mickeymotormount]

Thats really good info. I was having the same problem. Is there any wire specifics you can give me. Routing/ Splicing into what wire? Color of wires? Thanks!

Here's the schematics and a description of the operation of the transfer case for a '99 Silverado with the 6.0.. Following years may be the same or different. The 4 wheel drive wire is gray/black and is pinned at the red C-2 connector at location 16. From '03 on, it's the green connector(C-2) and the same gray/black wire at pin #16.









Still reviewing my '93 schematics to find out how I can ground this wire when I switch into 4 low. Stay tuned, I may be close to an answer.