Question for those with 4spd Manual - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Madbomber88 · 06-14-2004, 03:17 PM

I'm just about done putting in the new Painless wiring harness but am stumped by one wire I took out. What is the black single wire that connects on top of the transmission near where the back up lights connect? I can't figure it out.
Thanks.

71 CST

TRUCKPOOR · 06-14-2004, 04:08 PM

Wish I could help!! I just took apart a 72 1/2 ton Cheyenne Super that had a 4spd in it and there were 2 wires in the loom that went down to the tranny by the backup light switch. Only 1 was used and I didn't take the time to try and figure out the other one. Good Luck, Rob

3wbdriver · 06-14-2004, 06:03 PM

Is it possible it's a standard loom (equipment package doesn't matter), and the extra wire is for a neutral safety switch on an automatic equipped vehicle?

Madbomber88 · 06-14-2004, 06:09 PM

No, it's definitely for something because it has its own plug. The only reason I even ask the question is because the plug is broken, and I'd have to figure a way to get it back together. But if I can't figure out what it's for, I'm hoping it isn't that important and I can go without. The new harness does not have a matching wire for it.

Blazer1970 · 06-14-2004, 07:40 PM

That wire/switch is for the Transmission Controlled Spark (TCS) system. The switch grounds the wire when the tranny is in 3rd gear.

06-14-2004, 03:17 PM	#1
Madbomber88 Active Member Join Date: Mar 2004 Location: Virginia Posts: 169	Question for those with 4spd Manual I'm just about done putting in the new Painless wiring harness but am stumped by one wire I took out. What is the black single wire that connects on top of the transmission near where the back up lights connect? I can't figure it out. Thanks. 71 CST __________________ 71 Blazer CST 72 K20 Capt USAF

06-14-2004, 06:03 PM	#3
3wbdriver Registered User Join Date: Aug 2003 Location: West Central Louisiana Posts: 82	Is it possible it's a standard loom (equipment package doesn't matter), and the extra wire is for a neutral safety switch on an automatic equipped vehicle? __________________ '72 Blazer, 4WD, 350/4 spd. Affectionately known as "Da Beast" '04 Silverado (new daily driver) '00 Intrepid (wife's ride) It's a BLAZER dude! No options, no emblems, no a/c, no fancy shmancy. It's a BLAZER....

06-14-2004, 06:09 PM	#4
Madbomber88 Active Member Join Date: Mar 2004 Location: Virginia Posts: 169	No, it's definitely for something because it has its own plug. The only reason I even ask the question is because the plug is broken, and I'd have to figure a way to get it back together. But if I can't figure out what it's for, I'm hoping it isn't that important and I can go without. The new harness does not have a matching wire for it. __________________ 71 Blazer CST 72 K20 Capt USAF

06-14-2004, 07:40 PM	#5
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	That wire/switch is for the Transmission Controlled Spark (TCS) system. The switch grounds the wire when the tranny is in 3rd gear. __________________ Tim

06-14-2004, 04:08 PM	#2
TRUCKPOOR Registered User Join Date: Oct 2001 Location: Littleton, CO. USA Posts: 260	Wish I could help!! I just took apart a 72 1/2 ton Cheyenne Super that had a 4spd in it and there were 2 wires in the loom that went down to the tranny by the backup light switch. Only 1 was used and I didn't take the time to try and figure out the other one. Good Luck, Rob



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