Transmission dreamin'

[WCraigH]

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. I decided to test this idea using "DeskTop Drag Strip" simulation software.

As a realistic baseline I used the 1/4-mile drag strip road test results on a 1955 Patrician from a contemporary car magazine. Then I entered the relevent data into the simulation and got nearly identical results:

18.6sec at 76mph (road test)

18.4sec at 75mph (simulation)

Then I changed 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):

18.15sec at 76mph (GM 700R4)

18.27sec at 75mph (Mopar 727)

18.45sec at 76mph (GM TH400)

20.09sec at 74mph (GM PowerGlide)

By comparison with a manual transmission:

17.77sec at 78mph (B-W T-10 manual)

So, there's really not much difference! For grins, I then changed the torque converter to a steet performance varient (1800 stall, 2.35:1 multiplication, 4% slip):

17.59sec at 76mph (GM 700R4)

17.59sec at 76mph (Mopar 727)

17.64sec at 76mph (GM TH400)

18.57sec at 75mph (GM PowerGlide)

It should be noted that the specs (according to the road test article) for the Packard torque converter are 1650 stall, 2.90:1 max multiplication, 0% slip (lock up). I set the simulation for stock tires, average weather and conservative driver.

[Guest imported_Speedster]

Very Interesting, and a Little Surprising. <img src="http://www.aaca.org/ubbthreads/images/graemlins/cool.gif" alt="" />

I would have thought the Th400 would have been the best. <img src="http://www.aaca.org/ubbthreads/images/graemlins/crazy.gif" alt="" />

and I would have thought there would be bigger differences in them.

[WCraigH]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I'm out of reach of my references, but thought the Four Hundred (and Caribbean) had a higher stall speed converter. Could you provide a similar set of simulation results for the 400 hardtop? </div></div>

Way ahead of you Brian. I did the simulations, but didn't include them in the above. [color:"red"]IF the Carib/400 converter has an 1800 stall converter instead of the 1650 of the Pat, then:

18.42sec at 75mph (stock 55 Pat)

18.11sec at 75mph (stock 55 400)

[color:"red"]IF one "tunes" the 55 Pat for drag racing, i.e., mod 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:

16.33sec at 82mph

[color:"red"]IF one then swaps a 1956 Caribbean 374 for the 1955 352 (50hp more), the simulation produces:

15.57sec at 87mph.

As a point of reference, this is approaching off-the-showroom floor muscle car performance. Simulations sure are fun...and cheap! <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />