[97sonoma400]

Hey everyone, I just joined this forum and am in need of some ideas. A few months back I managed to get my hands on a "barn find" 1997 GMC Sonoma SLT stepside that somebody has installed a smallblock chev 400ci v8 into with an aftermarket 3 speed transmission (its a 'transco' if anybody has ever heard of them). after sitting for 8 years it started and ran with absolutely no issues- however the rest of the truck is a wiring disaster. none of my rear lights work properly (brake lights only work with lights off, reverse lights don't come on at all, signal lights are intermittent at best and dont work with lights on) and the front signal lights act the same as the back ones. The most confusing part to me is that my power windows only work with the parking brake on, and there's a click from behind the dash both when the brake pedal is pressed (which is normal) but also when I press the window switch. I'm thinking of just ripping the dash out and replacing the whole wiring harness. Does anybody have any advice or ideas on anything I can try before rewiring the whole thing?

 

[Jayhawke]

you have bad grounds. in the rear on the left side rail there is a wire that runs to a loop terminal bolted to the frame.up front there are (should be) grounds from rear of block to the firewall. that is in addition to the big three- batt to frame, batt to rad support and batt to block.as to the power window- sounds like the ground to your fuse panel/dash is compromised.

 

[bk2life]

Hey everyone, I just joined this forum and am in need of some ideas. A few months back I managed to get my hands on a "barn find" 1997 GMC Sonoma SLT stepside that somebody has installed a smallblock chev 400ci v8 into with an aftermarket 3 speed transmission (its a 'transco' if anybody has ever heard of them). after sitting for 8 years it started and ran with absolutely no issues- however the rest of the truck is a wiring disaster. none of my rear lights work properly (brake lights only work with lights off, reverse lights don't come on at all, signal lights are intermittent at best and dont work with lights on) and the front signal lights act the same as the back ones. The most confusing part to me is that my power windows only work with the parking brake on, and there's a click from behind the dash both when the brake pedal is pressed (which is normal) but also when I press the window switch. I'm thinking of just ripping the dash out and replacing the whole wiring harness. Does anybody have any advice or ideas on anything I can try before rewiring the whole thing?

If it’s been sitting for 8 years, you need to pull the fuel tank and replace it, or at least have it cleaned. It may start and run for a bit, but you’ll get a while world of sh*t in not much time. All the junk in the fuel tank will get into your fuel lines and the entire fuel system will get compromised.



Would like to see pics of the transmission. TRANSGO is parts supplied still today



Pictures of the truck helps immensely, as it’s hard to see what’s going on through words.



Is the engine carb? Fuel injected?



Welcome to the site, there are some people in here with lots of experience.



In all honesty, depending on the money you spent on the truck, anything that sits for near ten years will give you headaches. You might be better off buying something else in the long run.

 

[97sonoma400]

If it’s been sitting for 8 years, you need to pull the fuel tank and replace it, or at least have it cleaned. It may start and run for a bit, but you’ll get a while world of sh*t in not much time. All the junk in the fuel tank will get into your fuel lines and the entire fuel system will get compromised.



Would like to see pics of the transmission. TRANSGO is parts supplied still today



Pictures of the truck helps immensely, as it’s hard to see what’s going on through words.



Is the engine carb? Fuel injected?



Welcome to the site, there are some people in here with lots of experience.



In all honesty, depending on the money you spent on the truck, anything that sits for near ten years will give you headaches. You might be better off buying something else in the long run.

If it’s been sitting for 8 years, you need to pull the fuel tank and replace it, or at least have it cleaned. It may start and run for a bit, but you’ll get a while world of sh*t in not much time. All the junk in the fuel tank will get into your fuel lines and the entire fuel system will get compromised.



Would like to see pics of the transmission. TRANSGO is parts supplied still today



Pictures of the truck helps immensely, as it’s hard to see what’s going on through words.



Is the engine carb? Fuel injected?



Welcome to the site, there are some people in here with lots of experience.



In all honesty, depending on the money you spent on the truck, anything that sits for near ten years will give you headaches. You might be better off buying something else in the long run.

I have cleaned the fuel system already so no worries there. Unfortunately i haven't been able to take many pictures as i am only able to work on it for a few hours every couple months as i cannot keep it n the city with me. The engine is a 400ci Chevy small block v8 with a Holley350 turbojet carb. The previous owner (or even the guy before him) has redone most of the wiring harness by himself and unfortunately his wiring skills are.. subpar. I've been tracing useless wires and just trying to figure out how its all been slapped together for the last few months. The transmission has a little trouble shifting into reverse or drive when cold but luckily it seems to work fine otherwise.

 

[oldeerslayer]

Holley350 turbojet carb

Never heard of such a thing. Holley has a 350 cfm 2 barrel, mandated carb for some oval track racing sanctioning bodies. They do make a Street Avenger version for some reason. Why anyone would put a 2 barrel on a 400 is questionable. The whole point of big cubic inches is to flow lots of cubic inches of air/fuel mixture. Done efficiently it theoretically will make big power, but not if it can't breathe.
At low rpms it would make a good engine for an old MF tractor.

 

[bk2life]

small block v8 with a Holley350 turbojet carb..

Never heard of such a thing.

i'd bet money mr sonoma meant quadrajet, since that's a pretty standard GM carb for that period.

 

[mr_mojo]

I know I’m a little late to the thread; my apologies.
IDK how familiar you are with automotive electrical (me, not so much). I’m looking at a factory shop manual for my ‘85 (not Haynes or Clymer); it looks like it has a dedicated electrical section with schematics. Hard copy (I hate PDFs for stuff like this) is $70 at factory service manuals dot com.
I hope this helps.