Re: top speed for a 21 super clipper with 356 cu. in

Posted by Tim Cole On 2020/3/1 9:11:12

Increasing final drive ratios (decreasing numerically) does not increase top speed beyond the required power output. In other words, the higher ratios serve to reduce engine wear factors at cruising speeds. Thus, the normal practice in the old days was to select final drive ratios that resulted in the fastest top speed. With today's multi-speed transmissions wear factors are reduced via high final gear ratios that bring rpm down to the optimal 1900-2200 range. Some may find the Packard going faster in direct rather than overdrive.

And yes, I do think the top speed of the Ultramatic may actually be higher than the overdrive because of this.