TH350C Governor Pressure Switch
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
TH350C Governor Pressure Switch
A quick question for those who drive 80-82 Vettes with a lock-up convertor. Has anyone had any luck with changing to a higher pressure rated Governor Pressure Switch to cure the problem of the TCC toggling on and off at cruising speeds?
Thanks in Advance for any info at all.
Tim
Thanks in Advance for any info at all.
Tim
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
Thank You for your reply. Can you tell me what size pressure switch you switched to in your car? My car is fine until I'm cruising on the highway at around 65mph. After a little while it starts the on/off, on/off routine. Its driving me crazy... Thanks Again Tim
Melting Slicks
Joined: May 2003
Posts: 2,078
Likes: 283
From: Dyersburg TN
been a while since I looked at it, but I believe 50. The trans shop I got my parts from (Coleman Taylor) knew exactly what I was talking about and had the switch right there in stock. I only notice it shift on the open highway, not more in town lock/un-lock.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Oddly enough( or not) you can test those pressure switches with air to tailor the speed the TCC will lock. 50 PSI switch, and 50 MPH governor pressure. GM didn't install any way to measure governor pressure, but it's 1:1. 45 MPH=45 PSI governor pressure.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
Thanks Tim
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
This is going to sound silly- when the TCC starts it's lock/unlock thing, just touch the brake enough to turn the stoplights on. See if the TCC stops being stupid.
The ECM sees engine temp, throttle position, trans gear, speed, engine vacuum, and a gaggle of other stuff. It could be a easy as a bad brake switch, or be a sensor someplace that's feeling bad.
The ECM sees engine temp, throttle position, trans gear, speed, engine vacuum, and a gaggle of other stuff. It could be a easy as a bad brake switch, or be a sensor someplace that's feeling bad.
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
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
The brake switch was the first thing I checked and it seems to be fine. I'm leaning toward the pressure switch next because it not to expensive to change. I guess I will just try one thing at a time until I find the problem. I have heard that this is a very common problem with the 81 with auto. The car runs great but the on/off on/off irritates the heck out of me.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I haven't looked at a 350C, but some of GM's "C" trannys you could shim the TCC shift valve with a flat washer or two to raise the pressure holding it locked.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 1,058
Likes: 27
From: Eastern North Carolina
But I don't have a clue where I would put the washers, I know I can handle replacing the pressure switch and if needed the TCC sol. I'm thinking that it might be heat related considering that it only does it after a steady half a hour of cruising on the highway.
Thanks for the help...Tim
