need transmission wiring help!

[Dead Bunny]

I have a 91 2wd non-innercooled with a 727. I am missing the harness for the trans (don't ask how) and I need to figure out where these wires hook to the speedo and park/neutral switch. I scavenged half a harness from a 97 but the colors don't match up so I don't know where to splice them in. Also all the electrical diagrams I come across don't have the right colors or reference a 3 pin speedo, only a 2 pin.

colors for the park/neutral switch
vt/bk
gr/br
bk/w

colors for the speedo
or
w/or
bk/lb

the colors on the connector in the engine bay go as follows
thick BL
thick BK
br/y
w
vt/bk
w/or
gr/br
bk/wt

[Mark Nixon]

The 2 "spare" wires in the main harness are for the 4wd sensor.
It's pre-wired into the main harness and isn't in the trans harness unless the harness is pre-wired for the transfer case switch to hook to.

ALL speed sensors on our 1990-1993 Diesel trucks were 2 wire, with the exception of the '92 and '93 2 Wheel Drive Automatic trucks, which used the 3 wire sensor, with the large black plastic speedometer hole plug.

The 1991-1/2 INTERCOOLED two wheel diesel trucks used a morphodite automatic transmission harness.
It plugs in at the same place as the '92-'93 trucks do, near the fuel filter, BUT it utilizes the 2 WIRE VSS plug at the VSS, instead of the 3 wire.
The early 1991 transmission harness and the 1990 transmission harness are BOTH plugged in near the heater box (see OP's pic above).

Mark.

[Dead Bunny]

my truck was originally a 3 wire speedo. As far as I can tell the orange wire hooks into some sort of PCM. In my case that would have been for the ABS (which has been deleted). I got a chance to look under a 90 truck today and the wires on my harness make a lot more sense now.