Gm Th400

I bought a old chevy truck that has a GM TH400 transmission in it. The truck was not running at the time (project) I got the motor running but need to figure out the trans. Does the TH400 have a kickdown cable? If so were does it go on the trans. Were does the Speedo hook up? And there looks to be a vacuum value on the right side. Any Ideals?

You may have better luck trying a Chevrolet message board since Turbo 400 transmissions are not found in Oldsmobile Auroras, which is the subject of this message board. I once had a '57 Chevy with a TH400 but, I cannot remember the particulars of the kickdown linkage. Good luck!!

TH400 has an electric kickdown which is a 1/4" spade lug on the drivers side. 12 v input will down shift depending on rpm range. The Vacuum modulator is located on the passengers side and is connected to full manifold vac. It controls shift points during normal acceleration. The govenor (internal) controls WOT upshifts. The TH400 is the strongest auto 3 speed GM made and can be easily modified to handle 800+ HP with a little $$.

TH400 has an electric kickdown which is a 1/4" spade lug on the drivers side. 12 v input will down shift depending on rpm range. The Vacuum modulator is located on the passengers side and is connected to full manifold vac. It controls shift points during normal acceleration. The govenor (internal) controls WOT upshifts. The TH400 is the strongest auto 3 speed GM made and can be easily modified to handle 800+ HP with a little $$.


Does the manifold vacuum line have to be a hard line? Or can it be your average rubber vacuum line?

Rubber line is fine. It will degrade with age/exposure to fluids.