Wiring help gmc vs chevy - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Missyblue · 08-04-2018, 02:10 PM

Hey I need help. I have a 57 gmc and the precious owner bought a chevy wiring kit. The colors seem different so hoping someone can answer a couple questions
1. Will a Chevy harness work with my gmc gauges/lights/etc?
2. I was going to order a wiring chart should I then now order a Chevy chart for color coding?
3. Am I crazy and shoukd scrap it and do something else. They are just so expensive and this is a good set just Chevy
4. Any other thoughts to consider I'm forgetting

Thanks

**mr48chev** · 08-05-2018, 01:08 PM

There shouldn't be any difference in color coding on any GM vehicle. That has been one of the great things about working on GM vehicles as apposed to some other brands. If you are working on a circuit on a GM rig the wire color code is the same as every other GM rig.

dsraven · 08-08-2018, 01:27 PM

I haven't compared the two but do know the cluster looks different. the wires should still connect and work though. the guages may need the correct sending units though,if swapping a fuel tank or engine. ensure you get a harness made for generator or alternator specific to match your truck. otherwise you will need to do some wiring to make that work anyway. if using HEI or another ignition set up that is not stock you may need to swap some larger guage wire in some circuits as well. if removing the "step on" starter pedal then some more wiring and a different ign switch may be required because the original switch didn't have a "start" position. if upgrading the steering column for a newer tilt style or something with an automatic shifter integral then the plug for the signals will likely need some attention as well as the ign switch wiring (if the swith is in the column)
the lights should wire the same with the same colours as well, maybe the connectors on the ends of the pigtails will be slightly different but that is something you can easily overcome. gmc front signal/marker lights may need some extra length of wire to reach the lights that are in the "mustache" part of the front grille surround,not a big deal though. your truck isn't stock, engine/trans wise, correct? you may need to swap around some plug connection ends and wire lengths for certain sending units etc anyway. the lights should be pretty close though. the heater fan control should work, you will need to know if the new harness has provisions for a wiper motor switch if going electric, some were simply vaccum motors
I guess it all depends on what you are planning to use from the stock version of the truck compared to what the new harness has provisions for.

08-04-2018, 02:10 PM	#1
Missyblue Registered User Join Date: Jul 2017 Location: Fruita, co Posts: 243	Wiring help gmc vs chevy Hey I need help. I have a 57 gmc and the precious owner bought a chevy wiring kit. The colors seem different so hoping someone can answer a couple questions 1. Will a Chevy harness work with my gmc gauges/lights/etc? 2. I was going to order a wiring chart should I then now order a Chevy chart for color coding? 3. Am I crazy and shoukd scrap it and do something else. They are just so expensive and this is a good set just Chevy 4. Any other thoughts to consider I'm forgetting Thanks

08-05-2018, 01:08 PM	#2
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,710	Re: Wiring help gmc vs chevy There shouldn't be any difference in color coding on any GM vehicle. That has been one of the great things about working on GM vehicles as apposed to some other brands. If you are working on a circuit on a GM rig the wire color code is the same as every other GM rig. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

08-08-2018, 01:27 PM	#3
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 8,333	Re: Wiring help gmc vs chevy I haven't compared the two but do know the cluster looks different. the wires should still connect and work though. the guages may need the correct sending units though,if swapping a fuel tank or engine. ensure you get a harness made for generator or alternator specific to match your truck. otherwise you will need to do some wiring to make that work anyway. if using HEI or another ignition set up that is not stock you may need to swap some larger guage wire in some circuits as well. if removing the "step on" starter pedal then some more wiring and a different ign switch may be required because the original switch didn't have a "start" position. if upgrading the steering column for a newer tilt style or something with an automatic shifter integral then the plug for the signals will likely need some attention as well as the ign switch wiring (if the swith is in the column) the lights should wire the same with the same colours as well, maybe the connectors on the ends of the pigtails will be slightly different but that is something you can easily overcome. gmc front signal/marker lights may need some extra length of wire to reach the lights that are in the "mustache" part of the front grille surround,not a big deal though. your truck isn't stock, engine/trans wise, correct? you may need to swap around some plug connection ends and wire lengths for certain sending units etc anyway. the lights should be pretty close though. the heater fan control should work, you will need to know if the new harness has provisions for a wiper motor switch if going electric, some were simply vaccum motors I guess it all depends on what you are planning to use from the stock version of the truck compared to what the new harness has provisions for.



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