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?

no kickdown on a 400 they use the modulator (vac. line hook up there) is the truck a 4x4 its on the transfer case if its a 2WD its on the driver side rear of the case

no kickdown on a 400 they use the modulator (vac. line hook up there) is the truck a 4x4 its on the transfer case if its a 2WD its on the driver side rear of the case


The truck is 2WD. I see a modulator toward the rear passenger side of the trans and a small electrical thing on the rear driver side. Can the modulator use rubber vac. line or does it need to be a hard line.

you can use rubber but hard line woud be better

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?


The turbo 400 does use a kick down cable but instead uses a kick down solinoid which is wired to a switch that in your truck resides just under the dash above the gas petal. The turbo 400 like a 350 uses a vacuum modulator which is located on the passager side of the tranny..connect this to a manifold vacuum source. The speedo cable attaches on the drivers side just before the tail of the transmission.