Somebody told me my name came up here so, here is my experience with the Saginaw overdrive. Yes I did run one for years. It held up behind by my 302 with no problems whatsoever, about 45K highway miles and occasional dragstrip usage. So there is no problem whatsoever with durability.
If you understand how a TRUE overdrive works (and yes, there were special sections in the owners and shop manuals) you would know that free-wheeling is an on-demand function via a manual lockout cable. The tailshaft planetary gears, and the free-wheeling clutch, can only be engaged when the lockout lever allows the solenoid to move the blockers into position. So you have complete control over when you have free-wheeling, which is a very useful feature on flat ground (saves gas). Otherwise, you have a direct drive 4-speed transmission. And the factory wiring prevented abuse by including a speed governor. Bypass this feature at your risk.
Also, a lesser-known side benefit is that with free-wheeling engaged, the FW clutch synchronizes the entire transmission, allowing leisurely upshifts or downshifts without use of the clutch.
I really loved my overdrive, and the only reason for changing to a T5 was that parts for the OD are becoming hard to find. Solenoids, planetary gearsets and clutch cages are NLA from GM or aftrmarket sources. The T5 has better prospects. Time will tell how it holds up, but I know I will miss flicking that switch and watching the RPMs drop from 2400 to 1800.
- Jack
