73 Vette Detent Cable
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
On my '72 (TH400) the detent function is accomplished via a switch mounted on the accelerator pedal. When the accelerator is fully depressed, the switch is activated and 12volts is connected to the transmission detent switch - on a single wire, not a cable.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Further, that downshift switch (activated at the accel pedal) sends a 12vdc signal to a solenoid valve mounted to the underside of the valve body separator plate (inside the trans). You need to determine if that 12 volts is not being sent to the trans, or if the solenoid valve is not turning on when it gets that 12 volt signal. Both items need to function properly for the THM-400 to have a 'forced downshift'.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
Get in the car, leave the car door open, turn the ignition key on, then depress the gas pedal all the way to the floor. You should be able to hear the trans detent relay operate. If not, start trouble shooting the problem. If you are getting 12volts to the tranny, you have a bad detent relay in the tranny. Cost less than $20, and is easily replaced (you have to remove the tranny pan).
Instructor
Joined: Apr 2012
Posts: 227
Likes: 0
From: Clarksville Tennessee
I know it months after, but does anyone have a pic of the detent wires going to the brake switch? Whe I got my 73 last year noticed a black and orange wires on a female boot dangling and mangled. I figured it went to the tranny but the guy said it wasnt necessary cause it had a manual valve which it didn't cause i'm almost finished rebuilding it. Problem is I dont know where the wires connect in the cabin. Thanks fir any replies so late on the thread.
Safety Car
Joined: Aug 2001
Posts: 3,685
Likes: 202
From: Waterford Mi
The switch is on the back of the accelerator pedal. There are two wires that go through the firewall into the engine bay. The orange wire should attach to the trans. The gray wire goers toward the front and then up the hood. It opens the cowl induction door inside the hood at the windshield.