[Schurkey]

Originally Posted by 59safaricat

Reply's like this are why 4 speed hydros get a bad rap because people don't understand them.

Everything I know about the Hydra-Matic, I learned here:
https://ateupwithmotor.com/terms-tec...istory-part-1/

That same web site offers insight into several other transmission designs. VERY recommended.

Originally Posted by 59safaricat

The torus slips at idle,

Yes. I said the fluid coupling slips. My point being, a torque converter slips, but also has the ability to increase torque while it's slipping. In fact, the greater the percentage of slip, the greater the torque multiplication; typically a maximum of 2.x times the input torque when the slippage is 100%. The torque increase is a primary benefit. Slippage in the converter also produces heat, which is "wasted" energy. The fluid coupling slips, therefore it wastes some amount of energy, but does not provide any increased torque.

Originally Posted by 59safaricat

which quickly diminished at very low speeds. This was purposely engineered for an exceptionally smooth startup by the input torus of the fluid coupling running at a slower speed than the engine due to the reduction of the forward gear assembly.

Yes. The "big" fluid coupling runs at less than engine speed.

Originally Posted by 59safaricat

Slippage is almost negligible after shifting into 2nd gear.

That'd depend on throttle position, engine power, and vehicle weight 'n' gearing. The "Torque Splitting" feature also included would minimize slip, it functioned in 3rd and 4th.

Originally Posted by 59safaricat

Between this design and the split torque design, these early hydros are documented as being the most efficient automatic transmissions in existence until lockup torque converters came into play in the late 70's/early 80's.

"Documented" by who, and when? Given that Studebaker and Packard each had production automotive transmissions with lockup torque converters (Packard in '49, Stude in '50) I think your claim is not valid.

https://ateupwithmotor.com/terms-tec...up-converters/

Originally Posted by 59safaricat

The 350/400 transmissions are more INefficient than the first dual band transmission in 1939. GM switched to the Turbo Hydros because they were simpler, lighter, and cheaper to manufacture.

Absolutely simpler, lighter, cheaper, in large part due to having torque multiplication in the converter versus needing an additional very-low first gear, an additional planetary assembly, and all the friction material and control mechanism to shift four gears instead of three. Also smoother-shifting. And more-durable, even with much-longer service intervals. With hugely-increased torque capacity. In short, more sophisticated, even though they may be less-complex.

Nowhere in my previous post did I make claims for "efficiency", although I implied that the Dynablow was...not. The Hydra-Matic had issues with harsh shifts. The "top dog" at Buick called it "Hydra-Jerk". Dynaslip was specifically designed to be utterly smooth, which of course it achieved because there were no shifting gears in normal operation. The tradeoff for Buick was throttle response and losses in the torque converter. GM progressively engineered the harshness out of Hydra-Matic, but removing that tendency toward harshness was a major factor in replacing friction elements with a second fluid coupling in the "Dual-Coupling Hydra-Matic". Which then meant there were two fluid couplings with the potential to slip.

For the record, Buick and Chevrolet used a rear suspension design that was enormously heavy (unsprung weight); both Buick and Chevrolet used non-shifting, "Torque Converter" transmissions because a harsh shift would upset the heavy axle causing noise, vibration, etc. This didn't last long at Chevrolet, Powerglide was re-designed from a "pure" Torque Converter transmission to a two-speed automatic also using a simplified torque converter. Buick went through multiple generations of progressively-more-complex Torque Converter transmissions that did not shift, but used multiple converter turbines to drive multiple gear ratios hydraulically/progressively. Then Chevrolet brought back a Triple Turbine Dynaflow-like transmission in Turboglide. And that didn't last long.

Originally Posted by 59safaricat

The dual band/dual coupling hydros were a true GM design from start to finish by Earl A. Thompson, a Cadillac engineer. The Turbo Hydros were a Simpson based design first licensed by Chrysler (Torqueflite) and later by Ford (Cruise-O-Matic).

Ford licensed the Simpson gearset first, then sat on it for years. Chrysler put that concept into production first.

Calling the Turbo-Hydramatics "Simpson based" implies a basic misunderstanding of the work that Simpson did. Simpson designed gear sets; theoretical and prototype designs. The "Simpson" gearset you refer to involves two planetary gearsets sharing a common sun gear. The sun--planet--ring gear ratio can be the same between the two gearsets, or it can be different. The defining factor is the sun gear always turns at the same rpm on both planetary gearsets.

Yes, the Torqueflite and C4--C6 also used the "Simpson Gearset", but it's not like any of the gears are interchangeable, or that Ford--Chrysler--GM purchased the gears from "Simpson". The Simpson design for the planetaries does not preclude independent development of the clutchpacks, bands, or one-way clutches that control the way the Simpson gearset actually changes gears.

Further, Earl A. Thompson did not invent the fluid coupling. That was "borrowed" from
Hermann Föttinger, who patented fluid couplings and torque converters on or before 1905.

The Ford Model T used a planetary gearset (or two, or fifteen, I don't know how many.)

So--OF COURSE--there was borrowing of technology, both licensed and public-domain inside all of the transmissions; and--really--in pretty-much every consumer product ever developed.