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

wade · 10-05-2003, 10:49 AM

i think i have finally discovered that my switch that i mentioned before, is a tcs switch which is a transmission controlled spark switch. and not a reverse light switch, i still have other gremlins in the light area so i think it was just a ground problem, as it has been made clear that the reverse light switch is not on the tranny.
so my question is, i do have the tcs switch installed and i understand that this is only a emission control device to not advance timing while the truck accelerates in first and second gear. somebody hsa already installed a hei ignition in the truck.
it has an aftermarket edelbrock carb and intake. i cant find a solonoid that cuts off vacuum to the distributor. if i just plug off that tcs port on my tranny to stop the leak i have, and leave the tcs wire off will that effect my engine in any way? Iam pretty sure it wont, but wanna make sure.
thanks

BLACK AND BLUE 67-72 · 10-05-2003, 01:26 PM

I don't think that it would matter if you did that.

motoretro · 10-05-2003, 02:17 PM

Quote:

Originally posted by wade
i think i have finally discovered that my switch that i mentioned before, is a tcs switch which is a transmission controlled spark switch. and not a reverse light switch, i still have other gremlins in the light area so i think it was just a ground problem, as it has been made clear that the reverse light switch is not on the tranny.
so my question is, i do have the tcs switch installed and i understand that this is only a emission control device to not advance timing while the truck accelerates in first and second gear. somebody hsa already installed a hei ignition in the truck.
it has an aftermarket edelbrock carb and intake. i cant find a solonoid that cuts off vacuum to the distributor. if i just plug off that tcs port on my tranny to stop the leak i have, and leave the tcs wire off will that effect my engine in any way? Iam pretty sure it wont, but wanna make sure.
thanks

I have been running for 7 years with the TCS switch bypassed, pulling full time vacumn from port side of carb. No problems whatsoever. Had a off idle stumble before doing this and along with upping the initail timing to 12 btdc, truck runs great. 87 octane and 0 spark knock with no run on. Shifts are much firmer and have yet to drive a new truck with as precise a shift. You still need vacumn for the tranny so don't plug the line, just bypass it. The switch is designed to not allow full vacumn in firs 2 gears until your engine warms up, only allowing that to happen when trans is in 3rd gear. By bypassing the switch you have full vacumn at all times in all gears.

wade · 10-05-2003, 10:51 PM

grreat stuff thanks for the info, have already plugged the port. it stopped the leak and you right, there seems to be no ill effect to the truck.

mrein3 · 10-06-2003, 07:31 AM

I bought a used '72 turbo 350. I had it rebuilt before I installed it. When I got it all together it was leaking. When I looked under there with the engine running I could see it was leaking out of the tcs switch. I took it out and plugged the hole with a pipe plug. Problem solved. No ill effect to how the truck runs and drives.

BTW, that "hole" works good for the autometer tranny temp gauge temperature sender. That is what is "plugging" the hole now.

motoretro · 10-06-2003, 11:53 AM

The TSC "switch is actually a detent which sends a signal from trans when its in third gear to solonoid at passenger side, rear of valve cover location. This activates the solonoid to allow full vacumn when in proper gear.

wade · 10-06-2003, 01:00 PM

yes, iam thinking that the truck tranny may be different from stock. right now there is just a direct vac line from the carb to the distributor, so the soloniod if it was ever there is long gone.
i will let you know if something blows up!!!!!!

10-05-2003, 10:49 AM	#1
wade Registered User Join Date: Aug 2003 Location: calgary alberta, canada Posts: 21	tcs switch i think i have finally discovered that my switch that i mentioned before, is a tcs switch which is a transmission controlled spark switch. and not a reverse light switch, i still have other gremlins in the light area so i think it was just a ground problem, as it has been made clear that the reverse light switch is not on the tranny. so my question is, i do have the tcs switch installed and i understand that this is only a emission control device to not advance timing while the truck accelerates in first and second gear. somebody hsa already installed a hei ignition in the truck. it has an aftermarket edelbrock carb and intake. i cant find a solonoid that cuts off vacuum to the distributor. if i just plug off that tcs port on my tranny to stop the leak i have, and leave the tcs wire off will that effect my engine in any way? Iam pretty sure it wont, but wanna make sure. thanks

10-05-2003, 01:26 PM	#2
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	I don't think that it would matter if you did that. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

10-06-2003, 07:31 AM	#5
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	I bought a used '72 turbo 350. I had it rebuilt before I installed it. When I got it all together it was leaking. When I looked under there with the engine running I could see it was leaking out of the tcs switch. I took it out and plugged the hole with a pipe plug. Problem solved. No ill effect to how the truck runs and drives. BTW, that "hole" works good for the autometer tranny temp gauge temperature sender. That is what is "plugging" the hole now. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

10-06-2003, 11:53 AM	#6
motoretro Registered User Join Date: Jul 2003 Location: Mid-MI Posts: 110	The TSC "switch is actually a detent which sends a signal from trans when its in third gear to solonoid at passenger side, rear of valve cover location. This activates the solonoid to allow full vacumn when in proper gear. __________________ motoretro 1972 Chevrolet Custom 10 Lwb www.esivart.com/ebay/truck.gif

10-05-2003, 10:51 PM	#4
wade Registered User Join Date: Aug 2003 Location: calgary alberta, canada Posts: 21	grreat stuff thanks for the info, have already plugged the port. it stopped the leak and you right, there seems to be no ill effect to the truck.

10-06-2003, 01:00 PM	#7
wade Registered User Join Date: Aug 2003 Location: calgary alberta, canada Posts: 21	yes, iam thinking that the truck tranny may be different from stock. right now there is just a direct vac line from the carb to the distributor, so the soloniod if it was ever there is long gone. i will let you know if something blows up!!!!!!



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