The A500 ratios work with; big gears, small cams,decent performance stalls, and with a wide powerband. If you match it up, you can have a great combo.
With the overdrive you can run the gears your engine needs .... like 3.91s or a bit better. This brings the 1-2 shift earlier in the speed range, and so the engine has less windspeed to overcome at the lower rpm it shifts to.
For straightline acceleration;
Lets compare a stock LA318 with the A904 and 3.23s a typical combo.The power peak comes at about 4000, and you'll probably shift at 4500. The 1-2 shift will come at 40mph.
With the A500, say you run 3.91s, so 4500 will now be 30 mph. So not only does the A500 multiply your torque to a higher level,(10.71 compared to 7.91) it reaches shift-rpm 10 mph sooner.
Ok in second gear now. With the A904 your second gear roadgear is 1.45x3.23=4.68.
With the A500, it is 1.54 x3.91=6.02 being about 29% more TM, and the A500 is only bucking a 30 mph wind, compared to the 40 of the A904
In second now, the 904/3.23s will not hit 4500 until 69mph, whereas the A500/3.91 will hit 4500 at 54 mph; that is a lot of windspeed difference.
By the time you get up to cruising speed the 3.23s will get you 65=2660 @zero slip, could be 100 or so more under load, so say 2760.
Whereas the A500 will cruise at 65=2220 in loc-up, 2760=81mph.
So in this scenario the A500 is a clear winner.
