some electrical probs. 82 GMC sierra

82GMC91CIVIC · February 24, 2004

i just bought a 1982 gmc sierra classic a couple days ago. i paid 900 and this truck's main purpose is to be a beater until i get my civic running again.

the truck was originally a diesel but the owner before the previous owner swapped in a gas 350. ive looked it over and from what i can tell its pretty half ass.

1. the speedometer doesnt work.

there are two cables that go into the cab but not up to the speedometer. i traced both cables back to the transmission and one plugs into it while the other isnt connected at all. i just want to know which speedometer cable i need to use with this swap because the two i have are different.

2. i dont know how to switch between the two fuel tanks.

there is a switch on the dash that is a green two position one with about 4-5 wires coming out of it. i tried switching it but nothin happened. i just want to make sure this is the switch for the gas tanks and if its not what does it do?

3. mystery foot switch to the left of the brake pedal.

figured out the foot switch was for the highbeams. never would have guessed myself. thanks

i still dont know how to switch the diff though

i was informed that this truck has a two speed differential but once again the owner didnt know how to use it. i think this switch might do that but im not sure.

also related to this there are two fat black cables that arent connected to anything by the diff. and one fat black cable that looks like it should go to the battery.

by the way if it helps the engine is a 350 out of an 81 car (i was told) with a 3 speed automatic transmission. the truck is a 82 sierra classic dually 2wd.

any help would be greatly appreciated. sorry about the long post. ill have some pictures later if you guys like that stuff. (im from honda-tech.com)