The torque converter, at least the 3-4 speed TorqueFlite or similar torque converters, don't weigh much more, if any, than the complete manual transmission flywheel and clutch assy. Even though manual trans flywheel weights can vary. It's all "rotational weight", one way or another.
The lock-up torque converter operates as a normal torque converter. Once vehicle speed is high enough, an internal mechanical friction clutch is activated which "locks" the two sides of the torque converter together for greater fuel efficiency. When needed, it can also unlock when more power is desired (heavy throttle or "kick-down"), then re-apply when "cruise" mode is again possible.
A good friend bought a new '76 (or so) Charger SE 360 2bbl. After it got some miles on it but still in the factory warranty, it started ot have a harsh engagement into "R" from "P". He took it back to the dealer and they checked it out. Nothing wrong was found. But as he had been "nice about it", they eventually authorized a new Chrysler transmission for it. Later, it developed the same situation, but possibly a bit less.
Turns out, when in "P", Chrysler designed the torque converter to be locked-up. When another gear was selected, it would unlock. In my friend's case, it was not unlocking soon enough before "R" was engaged. Hence, the harsh engagement. His new routine became "P" to "N", then "R" so everything would be unlocked and engage as smoothly as an earlier TorqueFlite would. Apparently this was something which Chrysler worked on as my '80 Newport 360 2bbl didn't have this issue.
Initially, Chrysler would lock-up the converter at 27mph, leaving the rest of acceleration to the engine's torque output. But would unlock when part-throttle downshifts happened. By 1980, the lock-up speed had been raised to about 53mph, which was much less noticeable and worked better, in general, by observation.
Generally, Chrysler did not put lock-up converters on their HP engines or on vehicles with factory tow packages.
Historically, Chrysler TorqueFlite torque converters always had a "tight" feel to them that similar Ford or GM torque converters did not. By Chrysler's engineering data in their fuel economy pamphlets of '78 or so, the lock-up torque converter was good for about 3% greater fuel economy. Doesn't seem like a lot, but when everybody was looking for "bits", every little bit helped.
Enjoy!
CBODY67
