Backup Switch Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Craven93 · 02-27-2021, 11:17 PM

I have a 1972 C10 with a 350 engine and a 3 speed Muncie (Three on the tree). There is a switch at the base of the column that turns on the reverse lights. I had to adjust it to get them working correctly.

Ive been tearing things apart over the winter to do a little needed work. I pulled the transmission and replaced all the seals. While putting it back together, I was looking at the switch that's attached to the side cover. It's obviously a reverse switch of some kind, but I'm curious what exactly its for. There is only one wire going to it. It's difficult to trace it out at the moment, as I have the truck up in the air.

Anyone have a quick answer of what it's for and how exactly it works? I've included pictures of the two different switches as well as the 1 wire plug for the transmission one.

Thank you in advance.

**Steeveedee** · 02-28-2021, 12:45 AM

I can't tell where it is, exactly, on the transmission, from the pictures. If it isn't actually the back-up light switch, it's probably the switch for the Transmission Controlled Spark system. It would have been situated so that it completed a circuit that energized a solenoid and allowed vacuum advance to the distributor.

Craven93 · 02-28-2021, 09:10 AM

It rests against the shift lever shaft for 1st/reverse. There is a flat spot on the shaft. Since it's only one wire, it must complete the ground. Guess I will try to trace out the wire at some point.

BigBird05 · 02-28-2021, 10:35 AM

x2 on TCS switch. You can reify it by looking at the elect diag.

Craven93 · 02-28-2021, 10:48 AM

Thanks Steeveedee. After doing a little more research on what you suggested, I believe it is indeed the TCS. The help is much appreciated!

External · 03-02-2021, 11:10 PM

Hey guys, in picture #2, what do you call that part of the reverse light switch that is bolted onto the colum?
My column is not original. It was a 3 on the tree, but the PO switched it out for an automatic. I have no reverse lights. I have the green wire with the little silver box on it that would go to the silver bolted on box on the colum. What is it called, wonder if it could buy one and put it on??

Craven93 · 03-02-2021, 11:16 PM

I believe it's called a Neutral /Safety Backup Light Switch

BigBird05 · 03-03-2021, 12:37 AM

Neutral safety switch.

02-27-2021, 11:17 PM	#1
Craven93 Registered User Join Date: Aug 2020 Location: Johnston IA Posts: 8	Backup Switch Question I have a 1972 C10 with a 350 engine and a 3 speed Muncie (Three on the tree). There is a switch at the base of the column that turns on the reverse lights. I had to adjust it to get them working correctly. Ive been tearing things apart over the winter to do a little needed work. I pulled the transmission and replaced all the seals. While putting it back together, I was looking at the switch that's attached to the side cover. It's obviously a reverse switch of some kind, but I'm curious what exactly its for. There is only one wire going to it. It's difficult to trace it out at the moment, as I have the truck up in the air. Anyone have a quick answer of what it's for and how exactly it works? I've included pictures of the two different switches as well as the 1 wire plug for the transmission one. Thank you in advance. Attached Images

02-28-2021, 09:10 AM	#3
Craven93 Registered User Join Date: Aug 2020 Location: Johnston IA Posts: 8	Re: Backup Switch Question It rests against the shift lever shaft for 1st/reverse. There is a flat spot on the shaft. Since it's only one wire, it must complete the ground. Guess I will try to trace out the wire at some point.

02-28-2021, 10:35 AM	#4
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Backup Switch Question x2 on TCS switch. You can reify it by looking at the elect diag.

02-28-2021, 10:48 AM	#5
Craven93 Registered User Join Date: Aug 2020 Location: Johnston IA Posts: 8	Re: Backup Switch Question Thanks Steeveedee. After doing a little more research on what you suggested, I believe it is indeed the TCS. The help is much appreciated!

03-02-2021, 11:10 PM	#6
External Registered User Join Date: Jun 2018 Location: Louisiana Posts: 185	Re: Backup Switch Question Hey guys, in picture #2, what do you call that part of the reverse light switch that is bolted onto the colum? My column is not original. It was a 3 on the tree, but the PO switched it out for an automatic. I have no reverse lights. I have the green wire with the little silver box on it that would go to the silver bolted on box on the colum. What is it called, wonder if it could buy one and put it on?? __________________ '72 Chevy Custom Deluxe Highlander. Med Olive/White 350/200 ps,pb and Air Conditioning!

02-28-2021, 12:45 AM	#2
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,677	Re: Backup Switch Question I can't tell where it is, exactly, on the transmission, from the pictures. If it isn't actually the back-up light switch, it's probably the switch for the Transmission Controlled Spark system. It would have been situated so that it completed a circuit that energized a solenoid and allowed vacuum advance to the distributor. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-02-2021, 11:16 PM	#7
Craven93 Registered User Join Date: Aug 2020 Location: Johnston IA Posts: 8	Re: Backup Switch Question I believe it's called a Neutral /Safety Backup Light Switch

03-03-2021, 12:37 AM	#8
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Backup Switch Question Neutral safety switch.

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