MarkMontereyBay (10/26/2011)
...So I am just curious how/if a 3 speed OD could be made more livable and strong enough to deal with the new aluminum heads, cam, etc. 5 forward gears all synchro is my choice for now.Regarding the Borg Warner T-85 with an R-11 overdrive behind it . . .
Borg-Warner built OD units that used either 3 or 4 planetary gears. The 4 gear system is the strongest. It was identified as an R-11 unit.
These T-85/R-11 transmissions are strong enough that they were used behind the most powerful FE engines. Overdrive was offered behind the factory high performance 390s and 406s in 1961-2 and the mighty 427 of 1963-4. After the 4 speed became available in 1962 request for the OD transmission declined but it did function just as intended by taming the very low rear end ratios that were commonly installed in high-performance cars.Thought this might answer your strength question.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York