VSS Wiring

I recently changed to 33" tires and Im trying to correct my speedo. I found a company that makes a box you wire inline with the VSS and you can adjust the percentage of change to account for larger tires and gearing. However their system requires that one of the wires on the VSS be a ground in order to work.

Theres only 2 wires coming out of it but I can only trace them as far as the top of the transmission and then I cant seem to figure out where they go. I downloaded the rodeo repair manual and the wiring manual from that free site but I cant find any information and where the two VSS wires run.

Any ideas?

most if not all ground wires on isuzus are black wires. and i saw one reference that indicated the other for the vss was yellow. any help?

//bc

I checked quickly last night and one of them was red.