Posted to Transmission Forum on 12/5/2015
Re: Greatest Transmission Textbook
Remember this: The governor is the "speedometer" to the
valve body. It generates about 1 psi per MPH of road speed.
So, if you're at a stop sign standing still, you should have
0 psi governor pressure. If you are doing 30 mph, you should
have about 30 psi governor pressure.
All transmissions aren't EXACTLY 1 psi per 1 mph, but the
idea to remember is that they are ALL proportional to road
speed. If you have a governor with a pressure curve that's
made for a low rear end gear, say a 4:11 or 4:56 and you're
running a 3:08, you will have to go awfully fast to get a
Assuming the governor pressure curve is somewhere near close
to being right, throttle pressure OPPOSES governor pressure.
If you have too much throttle (TV) valve pressure, you will
have to create a lot of governor pressure to overcome it and
make the shift valve move.
This is really hard to describe in words, but think of it
this way" The 1-2 shift valve has a 15 lb. spring on it. On
the spring end of the shift valve is TV pressure. On the
opposite end of the shift valve is governor pressure. In an
oil schematic, governor pressure is blue and TV pressure is
With ZERO TV pressure, it will take 15 psi of governor
pressure to overcome the 15 lb spring and stroke the 1-2
shift valve to make a 1-2 shift. Make sense? -HOWEVER- If
the driver gives the vehicle a little throttle, say 15 psi
of TV pressure, now the governor pressure has to rise to
overcome the 15 pound spring PLUS an additional 15 psi of TV
pressure for a total of 30 pounds, or 30 psi of governor
pressure to make the 1-2 shift valve move. (actually 31 psi)
This is why a transmission shifts later and later as you
give it more and more throttle. It's the TV pressure going
up. There's no other way the transmission can know what the
driver is doing. It's all in the TV cable, it's adjustment,
and having the proper geometry at the carb/throttle body.
I hope it's clear as mud now. :-) Good luck!
Technical Information Specialist/Technician
Draper, Utah, USA
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