Like the author of the below article I lately ended up driving my trans in drive rather than overdrive except for highway periods. I just like the reduced shifting and better response of the engine, while rpms are still fairly low. It wasn't really until then that I realized at lower cruising speeds the converter would unlock in 3rd gear when I normally release the gas pedal, and whenever I step back on the gas it would lockup-just the other way around than you would expect it, and how it works at higher speeds and in overdrive. The most annoying part is that in certain situations if I slightly increase acceleration right after a 2-3 shift and subsequent lockup, engine rpm and torque drop to an extent that forces the trans to shift right back into 2nd, instead of just unlocking in 3rd first.
In the below article which I think is written pretty well, there is mention of a chip to program the torque converters lockup/unlock behavior. Does anyone have more details on this?
AXOD-E/AX4S | Taurus/Sable Encyclopedia