I was under the project car I am putting back together, 2 questions on the Turbo 350 Transmission.

1. On the right (passenger side) of the Turbo 350, are the in and out lines to the radiator cooler. One is low and the other above it. Which is the in and out ? And on the radiator cooler, which port is the IN.

2. Below the cooler ports is what looks like a vacuum valve/sensor with a 1/4" barb for a hose on the rear This screws into the transmission body. Where does the vacuum line go for vacuum ? Intake manifold or a port on the carb ?

And what is the purpose of this vacuum valve/sensor.

I have had my drivers license since 1959 and this is the first auto tranny vehicle I have ever owned.

Thank You
8Valve

 

I can't tell you how the factory configured the cooler lines on that year. However, the other item is a vacuum modulator. It should connect to manifold vaccum, either the manifold itself or the large rear port on some carbs (which is manifold). Don't connect it to the timed port on the carb; that's for vacuum advance on motors with EGR and other emission controls.

 

The TOP transmission line is the fluid OUT and the bottom line at the cooler is fluid IN. That valve you're speaking about is the transmission modulator valve and it gets it's vacuum from the #8 runner of the intake manifold (you'll see a fitting screwed into the top of the runner). The modulator valve allows soft low throttle shifts by regulating fluid pressure inside the transmission.

 

The modulating valve helps determine engine load. The more you romp on it the higher the line pressure in the transmission, the shift points shift harder

 

Thanks for the replies. Understand the in/out ports and the modulator.

Thank You
8Valve

 

Post #3 is incorrect and makes me recall a messy story a decade ago...
I had completed a fluid and filter change and wanted to flush the cooler and TC by pumping new fluid from the TH350 through the TC and cooler, and then, by attaching a long 3/8 hose to the return line, direct the outflow from this hose into a large bucket.

I had my wife, none too happy helping with garage work, observe the outflow (which I couldn't see since I was to run the engine for a few seconds) and yell at me to shut off the engine when the fluid became clean. I was unsure which was the outflow port on this TH350, but I had studied Ron Sessions book, the "Turbo Hydra-Matic 350 Handbook", which stated on page 14 that the return line was the bottom one on the transmission.

So, as she watched for flow out of the rubber line into the bucket I started the engine...
Five seconds, ten seconds passed - "Got any flow?" "No not yet!" Then 15 - and 20 seconds. I couldn't stand it any more and shut off.

As I came around to the passenger side of the car, I saw behind her a huge spreading spill of red transmission fluid on the garage floor which had flowed out of the open "return" port on the trans! Try to guess how many rolls of paper towels it takes to soak up a half gallon of fluid beneath a corvette on jack stands! It was NOT fun!

I rechecked the book and it is indeed INCORRECT! I marked this error clearly to avoid making it again. On the other hand, on page 90, there is a flow diagram which correctly shows with very tiny arrows that the bottom is outflow and the top is inflow (return).

Hope the same error doesn't catch you like it caught me. (Should have had a video of it - would have been good YouTube fodder!)

 

Top line is return from cooler

 

Larry;
Thanks for the update on Port Assignments.

8Valve