I have an ’85 C-10 pickup that we’ve installed a factory fuel-injected 5.3L truck engine. We bolted a TH400 transmission to the LS engine but I now realize that I don’t have any way to trigger the kickdown linkage on the TH400 trans. How do I do this so I don’t hurt the trans?
Jeff Smith: We’re going to assume that you have a cable-actuated throttle linkage for your 5.3L LS truck engine. We’ll also assume your pickup uses a cable throttle assembly – so it should not be difficult to build a small bracket that can mount a simple microswitch that would be triggered as the pedal linkage reaches wide-open-throttle (WOT). Chevrolet used a switch mounted off the throttle pedal assembly on a 1970 Chevelle to trigger the TH400 kickdown so you might be able to look at one of these mounts to get an idea how to make one.
With regard to wiring, it’s really simple. Place one wire from a switched, 12-volt positive source on one side of the micro-switch. Run a wire from the second connection on the switch directly to the electrical connection on the transmission. When the throttle hits WOT, the switch will complete the circuit and 12-volts will be supplied to the internal solenoid in the TH400 trans which increases line pressure and changes the shift characteristics of the trans. It’s that simple!
I recently had my th400 rebuilt in a 1988 GMC , before truck went in only slipped in 3rd gear. I got my truck back no problems shifting or slips but now my kick down switch not working at WOT.
Transmission guy is not wanting to take responsibility. What do I do any ideas?
I know kick down worked before
check the wiring and make sure it is plugged in and make sure the circuit is working on the out side and then it could be an internal solenoid issue.
Absolutely adjustable modulator valve helps get it all in sync
Asking away, ok I’m putting a 2000 ls 5.3 in my 84 c10 with a t400 trans and I’m wanting to have the 0411 pcm to know when it’s in park or drive to help with idle control when I decelerate . I’m getting a Dakota digital gear selector that mounts to trans shifter linkage my question is which pin/pins do I use on the pcm? There is like 3-4 on wiring diagram I’ve heard 1 wire to pcm one to ground others say 2 to pcm instruction on digital unit says hook up to neutral safety switch pin. I’m pulling my hair, don’t want to wire it up wrong and smoke pcm or digital unit. Any help with be appreciated