[1969_CM2590D]

Ok you guys got me all motorhead geeky here. I may be repeating stuff that a lot of you know, but for those that don't...

These GMC"S have the ORIGINAL Hydra-matic! No Park, no Drive (on the truck application- "D" on the cars, though), no torque converter. I've enclose a photo here of Hydra-Matic 1.0 in a 1949 Pontiac. Not to be confused with Dual-Range or Jetaway Hydra-Matic.The pawl that immobilizes the drivetrain is engaged with the engine off, then put in reverse. Full "Drive" is that "1-4" on the shift indicator. This last iteration of Hydra-matic 1.0 finally ended in the 1962 GM trucks.

This thing was stout. This is from Wikipedia:

The all cast-iron Hydramatic was the heaviest automatic transmission ever produced for automobiles. The heaviest of them all was the Truck Hydra-Matic version offered by GM Truck and Coach Division in its line of light- and medium-duty trucks and conventional buses, as well as with its transverse mounted gas L6 engined transit buses produced until 1963. That particular version weighed in at an incredible 655 pounds, when equipped with the angle drive for the transit bus application, while the ¾ ton and up pickup truck model (HM270) still tipped the scale at a solid 435 pounds. When coupled to GMC's heavy V6 powerplant of 1960-1962, the powertrain weight was not too much lighter than the weight of the entire body of a ¾ ton P-2500 model pickup truck. Even its successor, the Controlled Coupling Hydramatic was reviled by shop mechanics having to remove or reinstall such a unit, as they, too, were quite heavy when compared to other contemporary units. In the end, the true Hydramatic was rendered obsolete because of its cost, both in raw materials used as well as the machining needed. The successor, Turbo Hydramatic, was a much simpler, lighter and cheaper, if less efficient, transmission.

Anyone have the Owner's Manual section on this to post? I'd like to see it.

Obviously the transmission (and drivetrain) of choice for heavy duty, long life applications. An HD Powerglide pales..