reinhol

Hey there!
I just recently became owner of a 1989 Chevy Van G20 with a petrol 5.0 liter V8 small block and THM700-R4 transmission.
She sure is rough both on the outside and inside but I have great interests to turn her into a fine jewel of my own.
First of course, any tips and tricks for a new you could say classic Chevy Van owner?
Secondly, and this has been bothering me for quite some time already, the old cable speedo/odometer doesn't work with the mechanical 4-speed transmission. Any suggestions or ideas on what to do with it? I have seen both aftermarket speedos and conversion kits to make analog and digital work with each other.

Eager to hear any help thrown my way!
Kind regards!

rickyralph

Been wondering about this same thing for years; and posted on here awhile ago with no responses. I have a 1990 g20 and the speedometer runs at half even with a new speed sensor (no cable on mine) and the odometer stopped working. Going to start cruising some other forums.

oldchevy

Welcome from Florida. Have you checked to see if the cable is broken?

Triaged

Pre-1996 OBDII computers are a bit hard but there have been tools fir diagnosis out there for a while. Look up Win-ALDL (Assembly Line Data Link). You need a laptop, serial port or a good USB to serial adapter, and a cable that you have to make yourself. I made one ages ago with parts from RadioShack. Some simple soldering with very few and cheap components. You need this to see if the computer is getting the right number of pulses.