4 speed or 4 speed OD?

In a regular 4 speed the input and output shafts are locked together in fourth (turning the same speed). The power flow is in and out, effectively along the same shaft in 4th gear.

In the 4 speed overdrive, however, third gear is when the input and output are locked, but in fourth, the power all goes through the countershaft so that the output shaft can be "overdriven", and this occurs for extended periods of time, at highway speeds, and under a high power demand. This extra load puts more side thrust on the countershaft, and tends to wear out the countershaft needle bearings and the pin itself. Also, the side load tends to work the pin hole in the aluminum case, and because the input and output are turning a different speed in fourth the needle bearings between the two shafts, and the nose of the output where they ride tend to wear more.


Personally though, I like the overdrive 4 speed and have one that I intend to use in my next build. I love the 3.09 low, and the larger gear spread does not bother me. I think it is an awesome and affordable transmission for the street.