My 3T40 (formerly th125) goes right back into third gear when I shift from N to d on the highway. Then the TC locks up withing one second. The only time there is a bump or jerk is if the engine N rpm is too far off from D rpm (ie coasting > 55mph). But a simple blip of the throttle gets the engine close to driving rpm before I put it back in D. Blipping the throttle has become second nature, and N coasting is jerkless (except for the driver
).