vehicle speed sensor VSS Issue

[vertex]

I am in the process of hooking up the vehicle speed sensor VSS and I am having a strange issue. When I put the VSS into the transfer case the dashboard speedometer works fine but the computer is not getting a signal from the VSS. When I take the whole assembly out of the transfer case the in dash speedo works and the computer sees a signal from the VSS. I have the quarterhorse programmer hooked up so I can hook up my computer to the program and watch the VSS to see if it is working. Does anyone have any ideas, I am stumped.

One idea I had is that the cast iron transfer case is interfering with the sensor some how, the sensor is usually installed in an aluminum transmission.

 

[Viperwolf1]

Maybe the wires are swapped.

 

[brewchief]

Maybe the wires are swapped.

This, if one is grounded to the case it would lose signal when installed. Speedo might be isolated and not see that it's grounded.

Just a thought anyway, might be something different altogether.