i tried a couple forums to get answer to TCS switch and solonoid to find out its functions and are they really necessary, any help would be appreciated thanks, 70 chevelle w 350 engine and trans, auto on floor, thanks

TCS (transmission controlled solenoid). I believe it was another emissions band-aid. Typically the switch would receive an electrical signal from the transmission (high gear - 3rd and 4th on manual). The signal was converted to vacuum via the solenoid. The vacuum was connected to the distributor vacuum advance and would advance the timing when high gears were selected.

TCS (transmission controlled solenoid). I believe it was another emissions band-aid. Typically the switch would receive an electrical signal from the transmission (high gear - 3rd and 4th on manual). The signal was converted to vacuum via the solenoid. The vacuum was connected to the distributor vacuum advance and would advance the timing when high gears were selected.

In essence, that is completely correct! :thumbsup:

In the years of the TCS, there is a switch on the tranny somewhere (depending on type of tranny). All this switch does is provide a ground the solenoid, it's just a simple grounding switch, nothing more. The solenoid near the carb has a 12v source to it, then a second wire goes to the grounding swith on the tranny. Super simple.
As Mike mentioned, the solenoid is actuated when the tranny goes to its top gear. For example, on a Muncie 4sp, this grounding switch is in the 4th gear shifter shaft position. The solenoid, when actuated, supplied vacuum to the vac adv can on the distributor. That's the short version.
Today, the ONLY reason that I can see for installing and correctly connecting a TCS, would be for an absolutely correct restoration. Otherwise, remove it and throw it in the lake!!!!!!!!!!
Then dial in an acceptable curve in your distributor and connect the vac adv can to a MANIFOLD vac source and forget it. :thumbsup:

thanks guys that all i needed:hurray:

If it was only an emissions issue, why did '70 cars come with them? I thought the feds didn't come up with their silly car ruining schemes outside of California until the '71 model year? Anybody got a picture of a car with one installed?

Page 646 in the '70 Assembly Manual. Here's a '70 Big Block carb from www.carburetor.ca

http://www.carburetor.ca/carbs/HTML/gallery/QJets/7040200lfq.jpg

Same as my '70 350/300 inthat the vacuum port is located up above the fuel inlet. This is where the front TCS vacuum line ran to. I believe this is fulltime vacuum although its physical location suggests ported. Typically a Qjet has a manifold vacuum port on that 'tombstone' boss just above the idle mixture screw or on the base plate. The '70 was untapped. Qjets have crazy, crazy details........

Hi,
how can I distinguish the tcs plug an the connector of a TH 350C?
thanks