[U47]

Originally Posted by stevep

A 64 Caddy THM 400 was actually a Buick Nail Head trans with an adapter plate to bolt to a Caddy only bellhousing configuration. A 65-67 Caddy trans used their own Caddy specifica trans case. A 68-up Caddy trans will bolt to a Pontiac, Olds or Buick BOP pattern motor.

Steve, are you saying that Buick had the turbo-400 before Cadillac or 1964? Also I will have to check with this guy I know who has a 64 Cadillac T-400 in his 64 Pontiac ( bellhousing starter) to know for sure what it takes to get it in there.

Don

[Jack Gifford]

Originally Posted by stevep

How so?

Study a cross-section drawing of a Dual-Range Hydramatic and you'll see that the fluid coupling is "just along for the ride" in 3rd and 4th gear- totally mechanical torque path from flywheel to output shaft.

I also have doubts about the dual-coupling being the more efficient, since the torque path in 4th gear is through the front fluid coupling.

All the early Hydramatics (even the Roto) had the efficiency advantage of a variable-displacement front pump. Very few other automatic transmissions used this feature.

I don't understand why the RotoHydramatic's fluid element would not be categorized as a torque converter, since the "mulitiplier" element enables torque-amplification.

[Jack Gifford]

Originally Posted by poison heart

... you'll stumble across dozens of threads of people have problems with them...

Or... I'll find dozens of posts just like yours, and maybe a couple of posts relating actual experiences.

Lighten up- as I tried to do, by referring to the "Wikiphobia" comedy routine...

[U47]

Originally Posted by pontiac jack

Study a cross-section drawing of a Dual-Range Hydramatic and you'll see that the fluid coupling is "just along for the ride" in 3rd and 4th gear- totally mechanical torque path from flywheel to output shaft.

I also have doubts about the dual-coupling being the more efficient, since the torque path in 4th gear is through the front fluid coupling.

All the early Hydramatics (even the Roto) had the efficiency advantage of a variable-displacement front pump. Very few other automatic transmissions used this feature.

I don't understand why the RotoHydramatic's fluid element would not be categorized as a torque converter, since the "mulitiplier" element enables torque-amplification.

I can understand why some people have doubts about the front coupling, but I think it's best to know and call the front coupling a clutch that is either on or off, empty or full It does the same thing that the old dual ranges front clutch does. The main thing is that it does not drive the output shaft the way the big driven and drive torus does.
Roto unit is called a automatic with a fluid coupling because it's vanes are not curved like a torque converters. The curved vanes are the difference and not if it has a stator or not. Also remember that roto hydramatic drains and fills the coupling like the super does so that means it has three duties. 1. transmits power from engine to transmission and affords slippage so the car can be running while it's standing still. 2. It drains and fills to become a clutch. 3. Multiplies torque.

Don

[stevep]

Originally Posted by U47

Steve, are you saying that Buick had the turbo-400 before Cadillac or 1964? Also I will have to check with this guy I know who has a 64 Cadillac T-400 in his 64 Pontiac ( bellhousing starter) to know for sure what it takes to get it in there.

Don

Buick and Cadillac both had the 400 in 1964. DeVille and Eldorado had the 400, while the Series 62 had the Dual Coupling. The large engine full size Buick had the 400 and the smaller engine had the ST-300.

I have a 64 Caddy in my shop right now with a Nail Head THM 400.
The 1st year that a Cadillac trans would bolt to a 61-up Pontiac motor was 1968 (which had a long tail). The 65-67 Cadillac had a flat top bellhousing. The 64 Cadillac THM 400 has a short tail and it is a single range. Dual range 400 came out in 1965.

[stevep]

Originally Posted by pontiac jack

Study a cross-section drawing of a Dual-Range Hydramatic and you'll see that the fluid coupling is "just along for the ride" in 3rd and 4th gear- totally mechanical torque path from flywheel to output shaft.

I also have doubts about the dual-coupling being the more efficient, since the torque path in 4th gear is through the front fluid coupling.

All the early Hydramatics (even the Roto) had the efficiency advantage of a variable-displacement front pump. Very few other automatic transmissions used this feature.

I don't understand why the RotoHydramatic's fluid element would not be categorized as a torque converter, since the "mulitiplier" element enables torque-amplification.

I see what you mean. But with the front unit in reduction in 3rd, I wouldn't consider that locked up. I consider "locked up" when the engine and output shaft are turning at about the same speed. JMHO.

I do agree about the Roto coupling actually being a converter based on it's function. Since GM called it a coupling, that's just the way I think of it.

[Jack Gifford]

Originally Posted by U47

... best to know and call the front coupling a clutch that is either on or off, empty or full It does the same thing that the old dual ranges front clutch does...

No. It's not a mechanical drive. A fully engaged friction clutch is a true mechanical coupling. Since this was brought up during a discussion of efficiency, the distinction is not trivial.

[Safari Larry]

Wow, lots of good info here, I'm learning a lot. Thanks Don for the great lessons.

Originally Posted by stevep

I see what you mean. But with the front unit in reduction in 3rd, I wouldn't consider that locked up. I consider "locked up" when the engine and output shaft are turning at about the same speed. JMHO.

Steve, I think what Bill and Jack are referring to as "locked up" is that power is transferred mechanically through the transmission without going through a fluid coupling or torque converter -- where slippage and heat buildup can occur. At lest that's the way I think of it when they say the dual-range is "locked up" in third and fourth -- and I agree using that definition. Bill Hanlon told me about that a few years ago and I didn't believe him until I studied the trans' manual a bit. It doesn't seem to be well known, possibly because the trans' manual doesn't come out and say it, you have to study the power flow. The "locked up" third and fourth would make for efficiency in those gears on par with a manual transmission. The dual-range had a lot going for it but I recall reading somewhere that it was the heaviest automatic ever built for cars -- of course that didn't matter a lot when they used it in tanks or trucks. It was used for several years in trucks after it was discontinued in cars, for example in Bill Hanlon's '57 GMC.

[stevep]

They used Dual Ranges in Trucks until 1962.

Like I said, in this business, locked up means that the input and output are turning @ the same speed in direct drive.

[U47]

Originally Posted by pontiac jack

No. It's not a mechanical drive. A fully engaged friction clutch is a true mechanical coupling. Since this was brought up during a discussion of efficiency, the distinction is not trivial.

A fully engaged or disengaged SPRAG CLUTCH IS MECHANICAL TOO! What do you think that front coupling does in there?
Would you also tell me that a stick shift car with a hydraulic operated T/O bearing dosen't operate a mechanical clutch disc against a flywheel and pressure plate in it's operation?? Or that bands in a automatic transmission and friction clutches that are also operated hydraulically don't have a mechanical application?

Don

[U47]

Originally Posted by Safari Larry

Wow, lots of good info here, I'm learning a lot. Thanks Don for the great lessons.

Steve, I think what Bill and Jack are referring to as "locked up" is that power is transferred mechanically through the transmission without going through a fluid coupling or torque converter -- where slippage and heat buildup can occur. At lest that's the way I think of it when they say the dual-range is "locked up" in third and fourth -- and I agree using that definition. Bill Hanlon told me about that a few years ago and I didn't believe him until I studied the trans' manual a bit. It doesn't seem to be well known, possibly because the trans' manual doesn't come out and say it, you have to study the power flow. The "locked up" third and fourth would make for efficiency in those gears on par with a manual transmission. The dual-range had a lot going for it but I recall reading somewhere that it was the heaviest automatic ever built for cars -- of course that didn't matter a lot when they used it in tanks or trucks. It was used for several years in trucks after it was discontinued in cars, for example in Bill Hanlon's '57 GMC.

Hi Larry, A couple of A/T books I have say that in the shift from 3rd to 4th gear locked the forward p. gear assy at one to one. The coulping now only handled 25% of engine torque reducing silppage to a negligible amount.
FYI my A/T books and Pontiac service manuals refer to the Driven Toris and Driving Torus as fluid couplings. Dual Range "D" type, Super Hydramatic "P" type and Roto Hydramatic Model 5 and Model 10. In the manuals, all of the above transmissions the reference is to driven or driving torus. Roto is refered to driving and driven torus with a fixed stator.
All auto trans with a torque converter refer to these driven and driving elements as Trubine (driven) and pump (Driving) Or First turbine and second turbine.
The determining factor of which type of auto transmission ( fluid coupling type or torque converter type ) is defined by the design of the vanes. Straight vanes are in units like dual range, super hydramatic, roto hydramatic are called fluid coupling automatics. All cars with torque converters have vanes that are curved. For all the people who say roto has a torque converter just look at the vanes in a exploded view of one and see what description Pontiac or Olds calls it.

Don

[Bill Hanlon]

Originally Posted by stevep

They used Dual Ranges in Trucks until 1962.

... and in Rolls-Royce until 1966.

[stevep]

Originally Posted by Bill Hanlon

... and in Rolls-Royce until 1966.

I should have known that as I have done a few those!!

[Jack Gifford]

Notice: My post#22 contains an error. The Dual-Range Hydramatic in 3rd or 4th gear does have the fluid coupling in the power-path.