Pretty cool explanation on how a torque convertor works. From 1953

The easiest to understand explanation on torque convertors I've seen!

 

I like it when its drawn in crayon and explained Barney style for my understanding, good video!

 

Me too!

 

That's the basics of vortex flow thru a fluid coupling, but it's not a torque converter.

Here's "The Rest of the Story"

A Torque converter adds another element between the pump and the turbine, called a stator. The stator has vanes set at a prescribed angle, which re-direct the oil that is returning to the pump.

That returning oil, without a stator, works against the pump.

The Stator, splined solid to a shaft fixed to the trans case, re-directs the oil returning to the pump, so it actually helps the pump turn. This is how the unit modifies or "converts" the torque of the spinning oil, so it helps turn the pump, thus multiplying force.

Hence the name "torque converter"

Here is a video that helps understand that concept.


One of the secrets to why our little 9.5 inch converters work so well, is that I always select a stator that multiplies the torque more than a larger diameter converter will. For instance, a 12" converter has a "stall torque ratio" of about 1.2 to 1. My 9.5" units have an STR in the 1.8 to 2.2 range. So there is more torque to move your car, without changing anything in the engine combo or tuning.

A fluid coupling is horribly inefficient, it was the addition of the stator that made the automatic transmission a viable option for passenger automobiles. The Stator mulitplies torque, which reduces heat and slippage.. I suspect the heavy Army trucks in that video had a trans cooler about the size of the radiator in your GS.

JW

 

Yup. The original GM automatics needed four speeds because of the fluid coupling actually absorbing rather then multiplying torque. Chrysler actually had some manual transmissions with fluid couplings. Buick's Dynaflow was the first automatic to use a torque converter in 1948.

 

Interesting, thanks for "the rest of the story"

 

Jim, which of those internal components is different in a Variable pitch converter?

 

I've had two switch pitch TH425s in my '66 Toronado and in both cases, the car took off better in low stall. High stall just gave me more slippage and I needed more throttle to get the car moving.

Has anyone had a similar experience?

 

Were they the stock converters?

 

Oh yes, switch pitches work better when you nail the throttle from idle rather than blocking with the brake. Great video, I really liked the music. I wonder how long that guy chased that ball with the garden hose?

 

ST300/St400 Switch Pitch.

 

Yes.

 

Then that would be normal, the reason I asked is that PAE/Poston was destroying those converters for years with incorrect modifications to achieve some pie in the sky stall number. If you had one of them, in high stall and light throttle, the car would not hardly move. Buying one of those for a customer's car back in the 90's, was exactly why I got involved in selling converters in the first place. We got into duplicating the stator mods of the original Kenne-Bell KB 149 converter, and while we were there, we added either furnace brazing or silicon tig welding to strengthen the unit. I sold dozens of those converters to replace PAE units, with universally excellent feedback from customers.

On your stock coverter, in high stall the stator angle change makes the converter becomes more inefficient, that is the only way you get one of those big heavy converters to increase the stall speed. So it is normal for it to be "loose" feeling in high stall. I still like the VP for towing applications, with the big TH 400 converter, and of course for those cars that came with it from the factory, but for virtually all hot rods these days, your much better off with one of my 9.5" converters. They are built to be efficient, the small size is what allows the stall speed, so they never have that "loose" feeling.

 

I think my problem resides in the way the throttle switch is wired. When there is no foot on the gas pedal, it goes into high stall, to keep the car from pulling too hard at a red light. The problem is that it takes about 1.5sec for the stall to change, so when I take off normally, the TC is still in high stall. The 455 that's in it has plenty of torque to get the car moving in low stall.

My car right now has 3.20 gears and I find myself in 3rd gear most of the time, even climbing steep hills at 25MPH. I have a final drive with 2.73s, which I plan on trying. Hopefully playing with the governor (to get more use of the lower gears) and the S/P TC I won't have much of a performance loss. My car is a cruiser and I'd love to do long trips in it.

I'll keep you guys in mind. Thanks.

 

I have tried Bruce Roe's controller. As you say, his delay from when the brakes are activated was a problem for me too.

I would love to be able to go into high stall at higher RPMs (such as the equivalent of dropping half a gear from 3rd without downshifting), but unfortunately past a certain RPM range, the high stall goes away.

My car is on jackstands now awaiting a disk brake conversion, but when I have it running again I'll revisit the S/P issue.

Thanks.

 

How is the switch pitch "switched" between high and low stall?
I keep reading about the electrical end of it..... the switch and solenoid, but is the fluid redirected in the convertor, if it is, how?

 

Yup.. Works just like the detent solenoid.. When energized, the VP Solenoid blocks a fluid exit path, thus energizing the stator circuit, which re-directs oil to the stator piston, that moves and holds the vanes in the high stall position. That position is a steeper angle, which limits oil flow back to the pump, and creates the "high stall".


As bw1339 has stated, vane return back to low stall is not hydraulically driven, it relies on converter fluid flow to strike the vanes and push them back to the low stall position. That movement time is variable, it depends on how much fluid is moving in the converter, so at idle, or just off idle/light throttle, it will take a bit of time. Nothing can be done about that, it's just the way it works.

Mikel, I would recommend you move the control of the VP to a simple switch, I like another dimmer switch on the floor to click it on and off.. this will give you full manual control.

JW