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What if you could choose "whatever" transmission you wanted for your Packard V-8? What would be the performance difference compared to the stock Twin-Ultramatic? To test this idea "DeskTop Drag Strip" simulation software was used.
As a realistic baseline, the 1/4-mile drag strip road test results on a 1955 Patrician from a contemporary car magazine were used. When the relevent data (stock tires, average weather and conservative driver) was entered into the simulation, nearly identical results were obtained:
According to the road test article, the specs for the Packard Twin-Ultramatic torque converter for the Patrician are 1650 rpm stall speed, 2.90:1 max multiplication and 0% slip (lock up).
Changing just the transmission with a stock stall-speed (1200 rpm) torque converter (non lockup, i.e., 2.40:1 multiplication, 3% slip). Here are the results (best to worst):
So, there's really not much difference! By comparison with a manual transmission:
Then changing the torque converter to a steet performance varient (1800 stall, 2.35:1 multiplication, 4% slip):
Going back to the Twin-Ultramatic, the Four Hundred and Caribbean had a higher stall speed converter than the Patrician and Clippers. IF the Carib/400 converter has an 1800 stall converter instead of the 1650 of the Patrician, then:
Tuning the 1955 Pat for drag racing, i.e., modify the converter for 2000rpm stall, change rear gear to 3.90:1 (instead of 3.54:1), change rear tires to "High performance Street", change driver style to "agressive" (full throttle against the brakes) and runs it at Pomona, CA (sea-level excellent weather), the simulation produces:
For even more simulation fun, IF one then swaps a 1956 Caribbean 374 for the 1955 352 (50hp more), the simulation produces:
For even wilder combinations, see AACA Discussion Forum thread Transmission Dreamin'.