[rfmaster]

Originally Posted by mcbassin

RF,
I was about to order that inline vss like yours when I looked at links you posted about the speedo gears. I know you have covered this before about the the rear end gear ratio and tire size need to be known before you know which gear drive to put in the tranny. So my question, why not just change the speedo from a later model truck? they are readily available at the pull-a-part. The car vss can send info to the ecm and there should be a wire that sends info to the speedo right? It seems like you might even be able to reprogram the eprom to cover tire size? I really don't know what the truck gear ratio is or what size tire we are going with yet. I just don't want to order a bunch of new parts and then go with larger tires and find out the speedo is wrong. Thanks for your help,

Mike

Mike

That may sound as a good approach, but have you looked at what is involved at swapping in 87-90+ dash into 86 truck? Since I have not looked at all details I'll have to research this first before lunching into this adventure.

On the surface, the car VSS can feed its output into DRAC module used in later model trucks (90-91) to provide 2000ppm signal to ECM. DRAC module can be reconfigured to reflect your truck's tire size, rear end gear ratio. But there could be potentially be wiring harness differences (or not) between fully electronic instrument clusters (IC) and earlier IC that used spedo cable to drive odometer and speedometer. This is the area that I have zero first hand experience in. I would start by locating FSM for later year trucks and compare to '86.

Start another thread.... or search, since IFRC there were several documented instrument cluster swaps of this nature.

//RF