Plastic thing in oil pan?

On Chevrolets, "1980 only"* used a thermostatic vacuum switch to a vacuum/electric switch for lockup engagement. 81+ were done through the ECM.


* US market, gasoline engine


Hope this diagram helps, should show you how to wire it through the brake lamp switch to avoid stalling when stopping, and avoids the use of a toggle switch.

FWIW, the fender mounted switch on 1980 A/G body Chevrolet cars was on the left fender, about halfway back...on the steel inner portion, not the plastic liner.

Huh I had a 83 firebird with a vacuum switch on the firewall controlling the lock up and I thought it was factory or at least it looked it it was a 305/700r4 combo it did have the ecm intact so I guess a factory switch might be hard to find if they were one year only

GM used this setup on trucks that used the 700-R4 through 1984. I listed the part number, still available from RockAuto, etc. here: https://gbodyforum.com/threads/200-4r-tc-lockup-kit-build-your-own.58098/

ssn696 said:

GM used this setup on trucks that used the 700-R4 through 1984. I listed the part number, still available from RockAuto, etc. here: https://gbodyforum.com/threads/200-4r-tc-lockup-kit-build-your-own.58098/

Click to expand...

I knew I remembered seeing them on trucks so I wonder how the one on the firebird I had got there I read your thread that’s good info