GMC to Chevy headlight question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

CG · 08-11-2018, 03:04 PM

So when going from GMC to Chevy I know the headlight connections are going to be different. Will I need to change the entire underhood harness, or is there a headlight section only section that I can just swap out?

stsalvage · 08-11-2018, 03:26 PM

You will need to change the Core support.The GMC is made for 2 head lights not one

**Stocker** · 08-11-2018, 04:14 PM

As far as the wiring, just use the GMC's outer hi/lo connector for the Chevy's 7" hi/lo headlamps. The inner high-beam-only connector will not be used. If there's not a good way to remove those unused wires completely, I'd at least cap them off to prevent accidental grounding.

CG · 08-11-2018, 04:20 PM

I already have all I need sheet metal wise. Was just curious about the harness. Ok looks easy peasy as far as the harness goes.

I haven't totally decided on the core support yet. I have the correct one, but I also know the GMC support is easily modified for Chevrolet. Ill have to look and see what all I have bolted to the core support. Its an air truck and it has auxiliary battery.

4oldcars · 08-11-2018, 04:28 PM

Bare in mind that if you do as Stocker says, when you hit the dimmer switch you'll be in the dark.

CG · 08-11-2018, 04:28 PM

lol, oops

**Stocker** · 08-11-2018, 06:28 PM

Quote:

Originally Posted by 4oldcars

Bare in mind that if you do as Stocker says, when you hit the dimmer switch you'll be in the dark.

Explain please? Maybe I'm missing something, but the GMC's outer lamps operate as both high beam and low beam, selectable by the dimmer switch. Chevy's lamps are the same, having both high beam and low beam. They each use the same 3-prong connector (one common wire, one high beam wire, and one low beam wire). So why would you be in the dark?

**Ol Blue K20** · 08-11-2018, 06:38 PM

Quote:

Originally Posted by Stocker

Explain please? Maybe I'm missing something, but the GMC's outer lamps operate as both high beam and low beam, selectable by the dimmer switch. Chevy's lamps are the same, having both high beam and low beam. They each use the same 3-prong connector (one common wire, one high beam wire, and one low beam wire). So why would you be in the dark?

X2, you will still have high and low beams. There will be no darkness

CG · 08-11-2018, 07:01 PM

Ok so basically I should never ever question advice again that I get from Mike?

LOL!!!

**Ol Blue K20** · 08-11-2018, 08:00 PM

Quote:

Originally Posted by CG

Ok so basically I should never ever question advice again that I get from Mike?

LOL!!!

EXACTLY! !!!!!!!!!!!!

**Stocker** · 08-11-2018, 09:40 PM

Now if you guys could convince my wife about that.....

**Ol Blue K20** · 08-11-2018, 10:23 PM

Quote:

Originally Posted by Stocker

Now if you guys could convince my wife about that.....

I could try but she probably knows you a lot better than I do

**Stocker** · 08-11-2018, 11:37 PM

Quote:

Originally Posted by Ol Blue K20

I could try but she probably knows you a lot better than I do

After 47 years, I bet she does at that!

08-11-2018, 03:04 PM	#1
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,773	GMC to Chevy headlight question So when going from GMC to Chevy I know the headlight connections are going to be different. Will I need to change the entire underhood harness, or is there a headlight section only section that I can just swap out?

08-11-2018, 03:26 PM	#2
stsalvage Scrapper 1 Join Date: Jan 2007 Location: Riverside Calif Posts: 1,649	Re: GMC to Chevy headlight question You will need to change the Core support.The GMC is made for 2 head lights not one

08-11-2018, 04:14 PM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,497	Re: GMC to Chevy headlight question As far as the wiring, just use the GMC's outer hi/lo connector for the Chevy's 7" hi/lo headlamps. The inner high-beam-only connector will not be used. If there's not a good way to remove those unused wires completely, I'd at least cap them off to prevent accidental grounding. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

08-11-2018, 04:20 PM	#4
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,773	Re: GMC to Chevy headlight question I already have all I need sheet metal wise. Was just curious about the harness. Ok looks easy peasy as far as the harness goes. I haven't totally decided on the core support yet. I have the correct one, but I also know the GMC support is easily modified for Chevrolet. Ill have to look and see what all I have bolted to the core support. Its an air truck and it has auxiliary battery.

08-11-2018, 04:28 PM	#5
4oldcars Registered User Join Date: Jun 2004 Location: On The Beach, S C Posts: 613	Re: GMC to Chevy headlight question Bare in mind that if you do as Stocker says, when you hit the dimmer switch you'll be in the dark. __________________ 4oldcars Driving: 1971 Jimmy w/68 Chev front clip, 1953 Bel Air 2 dr hdtp, 1996 Roadmaster wagon, 2000 Eldorado The ones I let go: 1931 2 dr sedan, 1935 pick up, 1938 2 dr sedan, 1962 SS 454, 1963 409 wagon, 1970 short bed, 1972 short bed, 1972 sub, 1976 short bed, 1986 long bed, 03 short bed

08-11-2018, 07:01 PM	#9
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,773	Re: GMC to Chevy headlight question Ok so basically I should never ever question advice again that I get from Mike? LOL!!!

08-11-2018, 09:40 PM	#11
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,497	Re: GMC to Chevy headlight question Now if you guys could convince my wife about that..... __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay



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