Transmission switch? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DT1 · 12-12-2010, 12:33 PM

I tried posting this in the engine section but didn't really get my question answered. I guess my question really is...Does a TH350 have a switch on it?
71 C-10 350/350
I'm in the process of reinstalling my engine and transmission.
I have a 16 gauge black wire that comes from a relay on my firewall. The diagram shows it going to a transmission control switch. The transmission is a TH350 and I can't see a switch anywhere on it. Does anyone know where this wire connects to?
Thanks!

bobjob · 12-12-2010, 12:50 PM

if i remember right ,, a th 350 has a vacuum modulator ,, not a trans control switch .. 71 was not computer controlled .. th 400 was electric kick down ..

piecesparts · 12-12-2010, 12:52 PM

There is no transmission switch on the TH350 tranny. There is a vacuum tube that runs down to the modulator on the passenger side of the tranny and that is all.

**VetteVet** · 12-12-2010, 04:27 PM

If the transmission is not stock it might be a th350C with the lock-up converter.I think they came out in 1980. The wire for the lockup comes from the fire wall relay an is vacuum controlled.

There was also a transmission controlled spark emissions system on the 71 models that had vacuum controlled relays and wiring to the transmission to control the vacuum advance on the distributor.

**Boog** · 12-12-2010, 04:34 PM

Wasn't there a spark control solenoid hooked to the trans for emissions in 72?

Sarge and I were both on it.

Longhorn Man · 12-12-2010, 04:36 PM

I *think* the TCS came out in 70... but yeah, the relays and wires were stock, it went to a switch that was on the side of the trans (both TH350 & 400). Odds are it started leaking and was removed with a pipe plug put in its place.

camaney · 12-12-2010, 08:13 PM

On my 70 Th350 I took out yesterday there is a two prong electrical connector what does that do?
Posted via Mobile Device

Longhorn Man · 12-12-2010, 08:46 PM

TCS, Transmision Controled Spark.
An early poorly designed emissions control piece. There was a temperature sensor in the passenger side head, and a switch in the tranny. The system would require the engine to be up to operating temperature, and the trany in top gear before it would allow vac advance to the dist..
It resulted in poor performance and reduced MPG. Most have been removed many many year ago

DT1 · 12-12-2010, 09:48 PM

Quote:

Originally Posted by Longhorn Man

TCS, Transmision Controled Spark.
An early poorly designed emissions control piece. There was a temperature sensor in the passenger side head, and a switch in the tranny. The system would require the engine to be up to operating temperature, and the trany in top gear before it would allow vac advance to the dist..
It resulted in poor performance and reduced MPG. Most have been removed many many year ago

Ok,
Thanks for the replies.
So, I have a wire from the relay that's supposed to go to the non existent switch on the transmission. I suppose I should just cut the wire and forget about it??

Longhorn Man · 12-12-2010, 10:18 PM

thats what I did, all that crap hit the shop floor pretty soon after buying it.

12-12-2010, 12:33 PM	#1
DT1 Registered User Join Date: Oct 2009 Location: Gardnerville Nv No Mo Cali!! Posts: 869	Transmission switch? I tried posting this in the engine section but didn't really get my question answered. I guess my question really is...Does a TH350 have a switch on it? 71 C-10 350/350 I'm in the process of reinstalling my engine and transmission. I have a 16 gauge black wire that comes from a relay on my firewall. The diagram shows it going to a transmission control switch. The transmission is a TH350 and I can't see a switch anywhere on it. Does anyone know where this wire connects to? Thanks!

12-12-2010, 12:50 PM	#2
bobjob Registered User Join Date: May 2009 Location: florence arizona Posts: 53	Re: Transmission switch? if i remember right ,, a th 350 has a vacuum modulator ,, not a trans control switch .. 71 was not computer controlled .. th 400 was electric kick down .. Last edited by bobjob; 12-12-2010 at 12:51 PM.

12-12-2010, 12:52 PM	#3
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Transmission switch? There is no transmission switch on the TH350 tranny. There is a vacuum tube that runs down to the modulator on the passenger side of the tranny and that is all. __________________ Frank Last edited by piecesparts; 12-12-2010 at 12:52 PM.

12-12-2010, 04:27 PM	#4
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Transmission switch? If the transmission is not stock it might be a th350C with the lock-up converter.I think they came out in 1980. The wire for the lockup comes from the fire wall relay an is vacuum controlled. There was also a transmission controlled spark emissions system on the 71 models that had vacuum controlled relays and wiring to the transmission to control the vacuum advance on the distributor. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

12-12-2010, 04:34 PM	#5
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,146	Re: Transmission switch? Wasn't there a spark control solenoid hooked to the trans for emissions in 72? Sarge and I were both on it. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross Last edited by Boog; 12-12-2010 at 04:36 PM.

12-12-2010, 04:36 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Transmission switch? I think the TCS came out in 70... but yeah, the relays and wires were stock, it went to a switch that was on the side of the trans (both TH350 & 400). Odds are it started leaking and was removed with a pipe plug put in its place.

12-12-2010, 08:13 PM	#7
camaney Registered User Join Date: Feb 2008 Location: sacramento california Posts: 201	Re: Transmission switch? On my 70 Th350 I took out yesterday there is a two prong electrical connector what does that do? Posted via Mobile Device

12-12-2010, 08:46 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Transmission switch? TCS, Transmision Controled Spark. An early poorly designed emissions control piece. There was a temperature sensor in the passenger side head, and a switch in the tranny. The system would require the engine to be up to operating temperature, and the trany in top gear before it would allow vac advance to the dist.. It resulted in poor performance and reduced MPG. Most have been removed many many year ago

12-12-2010, 10:18 PM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Transmission switch? thats what I did, all that crap hit the shop floor pretty soon after buying it.



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