Re: Ultramatic by Borg-Warner?

Posted by Tim Cole On 2015/1/14 16:12:32

The second turbine in the Ultramatic was not the same as in the dual ratio Dynaflow. The second turbine in the Dynaflow used a planetary gearset to provide reduction. The second turbine in the Ultramatic was merely an attempt to compound the directed force. Modern torque converters don't use them because they are not efficient.

The need for the direct clutch to prevent problems during coupling phase is not a change in ratio. Without the lockout the converter will slip with higher power loss than a torque converter with lower blade angles. Buick used a solenoid operated two range stator to offset this problem. The so-called "Switch Pitch" Dynaflow would increase the angle for acceleration and reduce it for cruise.

A comparison between the original Powerglide and Ultramatic is shown below. Even after correction for the power to weight ratio, the Ultramatic torque converter is more efficient at low speeds and less efficient at high speeds. The forced lock out at 56 mph for the Packard means these figures are a comparison of torque converter efficiency. The Packard is faster at breakaway (even after correction for power to weight) but the Powerglide is more efficent the higher the speed. So the direct clutch in the Packard eliminates this problem.

...........1951 Chevrolet.................1951 Packard 300
.............Powerglide

Horsepower........105............................150

Weight...........3405...........................4380

LBS/HP...........32.4...........................29.2

0-60 mph High..24.84........................20.80
.Low and High..20.15........................18.30

0-30.....Low.....6.8............................5.4

Mileage at 60.....19...........................13.6


Hope this helps explain what is going on.