1. Home
  2. Automotive Technologies
  3. th400 transmission not shifting

th400 transmission not shifting

I have recently swapped out my tbi for edelbrock multi-port fuel injection on my 454 1 ton chevy. I removed my factory ecm computer to install edelbrocks computer. Well I have a th400 that wont shift automatically because that little orange wire that comes off of the tranny is just hangin there. I couldnt find a kickdown switch at all on my throttle on the tbi or on the gas pedal in the cab. I know theres a transmission relay on the firewall. According to mitchells wiring diagrams the little orange wire goes to the transmission relay then to the computer I no longer have. Is that correct and if so what can I possble do to get transmission to shift. Any help would be great because Im totally stumped.

Reply to
yblow
Loading thread data ...

The electrical connection is used strictly for forced downshifts, it won't affect the shifting if disconnected. The vacuum modulator controls the upshifting, I suspect your change to TBI has somehow interrupted the vacuum supply to the modulator.

Reply to
John Kunkel

Im sorry it will still shift I just dont have any forced downshifts.

Reply to
yblow

If Edelbrock doesn't offer a solution and there's nothing in any of the speed parts catalogs, you're probably going to have to scrounge the junkyards and find something off of a mid 80s pre-TBI truck. 'Something' being the electrical switch that mounts on the gas pedal bracket.

Reply to
aarcuda69062

You know whats funny I just did some reprogramming on the edelbrock tuner and its getting to shift a lot better with out that wire hooked up. But according to those mitchell wiring diagrams that orange wire supposibly goes to a relay and then goes to the slot on the factory computer that it says goes to to the brake switch. So Im wondering if that wire is just downshifting when I step on the brake. It is a 1 ton pickup.

Reply to
yblow

Does it have a lock up torque converter? Many of them have sense wire from the brakes that unlocks the TC when the brakes are applied

Reply to
Ashton Crusher

You know I have no idea if has a lock up converter or not. I not even sure what a lock up converter does Im not to smart when it comes to transmissions?

Reply to
yblow

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.