Quote:
Originally Posted by steve25
if there was a way to drain the converter then that would explain the added usage of the fluid!
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The original, and the later dual-coupling Hydra-Matic don't have a torque converter. They use a more-prehistoric "fluid coupling"; almost certainly with an easy-access drain plug that the bean counters removed from most torque converters.
Of course, when the service interval for fluid changes is as short as it was for the Hydra-Matic transmission and crappy 1940s--1950s fluid, extra drain plugs are a distinct advantage.
That's probably why they have four speeds, instead of three--no torque multiplication from a torque converter, just
slip from a fluid coupling. The later unit had
two fluid couplings--the main one in front, about the same size as a typical torque converter, plus another that took the place of a clutch-pack. About 8" diameter, with a fill-and-drain scheme to mimic a clutch pack applying and releasing.
Wanna really blow your mind? GM built 8- and 21-speed variations of the Hydra-Matic for trucks.
https://www.curbsideclassic.com/auto...plex-dead-end/
The original Buick "Dynaflow" (Dynablow, Dynaslow, Dynaslip) was a "torque converter transmission". That is to say, it was not an "automatic" transmission in that there was no automatic gear changes--it started out, and stayed, in "high" gear unless the driver moved the shift lever to "low". The only torque multiplication you got without self-shifting was what the converter could provide. Later versions of the Buick trans were more sophisticated but still didn't move the vehicle all that well.
It's no wonder that the Turbo-Hydramatic 400/Super Turbine 400 was such a ginormous improvement in sophistication from the day it debuted in Model Year '64.