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TCS switch
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The switch on the transmission is there to 'tell' the TCS system when it is in high gear ranges (3rd for auto; 3 & 4 for manual). The TCS system is functional [retards engine ignition so engine runs hotter and burns off more hydrocarbons] at idle and low cruise speeds; the tranny switch turns the system "OFF" at upper gear range(s).
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,353
From: Santa Ana CA
The TCS simply does not allow the distributor vacuum advance to work in 1st and 2nd gears when the engine is operating within its normal temperature range. The solonoid essentually keeps the vacuum signal from getting through.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
There is also an additional sensor/switch ***'y mounted on the passenger side cylinder head. This component allows manifold vacuum to reach the distributor during either high or low coolant temp conditions irrespective of all other conditions.
The entire system was filled with a 70% solution of PFM* on both the pneumatic and electrical sides prior to leaving the factory thereby ensuring future generations would be baffled by it's true function and purpose.
*pure farquing magic™
The entire system was filled with a 70% solution of PFM* on both the pneumatic and electrical sides prior to leaving the factory thereby ensuring future generations would be baffled by it's true function and purpose.
*pure farquing magic™
Intermediate
Joined: Nov 2008
Posts: 31
Likes: 0
From: Tampa FL
I have also wondered if my 75 auto with Holley 600 would run better if I had a TCS set up. I was not given all the parts when I bought the car. I got a RPM Performer intake and used one of the 600 Holleys the guy had attached to a double pumper. The vacuum line to the tranny is metal and was rigged up from the carb. The car always seems to never get out of 2nd. Did 75 change something or is it the same as your 74?
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The TCS system will not make any engine system run 'better'. It was there strictly for emissions control purposes. It caused the engine to run hotter than it needed, used more fuel than it needed, and confused more folks than did Salvadore Dali.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Mike, you slay me. That's the best explanation yet!
cc
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Actually, I equate the TCS system to the C5 skip shift system because they both are easily defeated by using more fuel.
With the TCS system WOT causes it to allow vacuum advance and with skip shift just don't shift until you reach 20 mph (a short trip in any Corvette).
Personally, I bypassed my TCS system preferring to stick with my 8 mpg instead of flooring it all the time.
cc
With the TCS system WOT causes it to allow vacuum advance and with skip shift just don't shift until you reach 20 mph (a short trip in any Corvette).
Personally, I bypassed my TCS system preferring to stick with my 8 mpg instead of flooring it all the time.
cc
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
The best part is when the pressure switch on the side of the trans decides to leak. A TH350 in 3rd will pump dry in less time than you think. and it spits fluid right out on the exhaust too.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Don't mean to hijack.
I have also wondered if my 75 auto with Holley 600 would run better if I had a TCS set up. I was not given all the parts when I bought the car. I got a RPM Performer intake and used one of the 600 Holleys the guy had attached to a double pumper. The vacuum line to the tranny is metal and was rigged up from the carb. The car always seems to never get out of 2nd. Did 75 change something or is it the same as your 74?
I have also wondered if my 75 auto with Holley 600 would run better if I had a TCS set up. I was not given all the parts when I bought the car. I got a RPM Performer intake and used one of the 600 Holleys the guy had attached to a double pumper. The vacuum line to the tranny is metal and was rigged up from the carb. The car always seems to never get out of 2nd. Did 75 change something or is it the same as your 74?
I can't see how adding a TCS would improve your runnability. But again, as above, I can't figure it out so perhaps I am off-base.
As for not shifting into third, automatic transmissions are too complex for my mind to grasp.
Melting Slicks
Joined: Nov 2003
Posts: 2,668
Likes: 118
From: St. Charles Mo
CI 5 & 8 Veteran
TCS is a terrible and archaic way of controlling timing. The only reason I have it on the LT-1 is to satisfy the originality buffs. I don't tell them that I secretly by passed the damn thing.
I am a EFI zealot, so if you think about it, an engine is calibrated to have an optimum fuel and advance setting given a MAP/RPM condition (i.e map cell). It's tough enough to get an accurate timing setting trying to combine vac and mech advance on the old distributors across the map, let alone adding another factor to change the setting depending on what gear you are in.
Its a built in error that cannot be accounted for. Performance suffers. 
Bullshark
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
You have:
-the TCS solenoid on the intake with manifold and ported vacuum spouts
-the vacuum advance can connecting to the above
-a temp switch/sensor between cylinders 6 and 8 in the passenger cylinder head
-a switch on the transmission
-some kind of delay switch on the firewall (I have never found it)
me
-the TCS solenoid on the intake with manifold and ported vacuum spouts
-the vacuum advance can connecting to the above
-a temp switch/sensor between cylinders 6 and 8 in the passenger cylinder head
-a switch on the transmission
-some kind of delay switch on the firewall (I have never found it)
me
Thread Starter
Intermediate
Joined: Sep 2009
Posts: 26
Likes: 0
From: Wichita KS
Always a relief to know I did not ask a stupid question to begin this thread. In short, I am surmising from the thread that if I just forget about whether mine is working or not, I should not detect a problem at idle as a result.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Well, that's hard to tell. With TCS 'active', there will be no vacuum advance in lower gear ranges. Of course, at WOT, there is no vacuum..so that's no big deal. Most folks who want to leave the hardware on the engine, just "manipulate" a couple of hoses so that the vacuum can is hooked up directly to a manifold vacuum fitting on the carb for 'normal' operation. Then, for shows or other 'originality' needs, switch the hoses so that the vacuum feed line goes into the TCS solenoid and the advace can line goes to the other solenoid connection. (what the other poster called "by-passing" the system)
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Well, that's hard to tell. With TCS 'active', there will be no vacuum advance in lower gear ranges. Of course, at WOT, there is no vacuum..so that's no big deal. Most folks who want to leave the hardware on the engine, just "manipulate" a couple of hoses so that the vacuum can is hooked up directly to a manifold vacuum fitting on the carb for 'normal' operation. Then, for shows or other 'originality' needs, switch the hoses so that the vacuum feed line goes into the TCS solenoid and the advace can line goes to the other solenoid connection. (what the other poster called "by-passing" the system)