47-59 B/W R10 Overdrive Operation Question

[SanJosesSteve]

I want to add an overdrive to my 270 motor with 3 speed transmission. I have the Official Guide B/W R10 overdrive book by Randy Rundle. It states that when the overdrive electrical components are functioning properly, it never free wheels below 28mph.

My question is, will pulling the handle under the dash immediately disable the system and restore direct engine braking, if so, can the handle be pulled at any time, under any operating condition? It’s not explicitly spelled out in the book.

While free wheeling under 28mph seems reasonable, I know of several twisty steep mountain roads here where 28mph would seem really fast and potentially boil your brake fluid before getting off the grade. -Steve