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On my 2009 S40 T5 AWD automatic, when I downshift at highway speeds (mid throttle or so), the RPMs increase and then decrease a bit, almost as if the downshift occurs then the lockup torque converter engages (?).

AFAIK it has always done it and when I asked the dealer about it a while ago they said they test drove it and that it behaves like all other S40s.

Any thoughts? Which gears have the lockup and when does it happen? In other cars I've had the lockup torque converter only appears to work in the highest gear.
 

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The lockup torque converter operates in any gear. If you accelerate gradually, you can feel 6, 8 or even 10 rpm changes as the transmission first shifts up, then the TQ locks. The TQ unlocks before shifting at each step.

On downshift, I'd certainly expect the TQ to unlock first. You'd have a very jarring experience, and the tranny too, if it didn't. But, once stabilized I'd expect it to relock for efficiency and better engine braking.
 

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Sounds normal; timing is everything to avoid any jarring feeling.

Learning to drive the GT and keep it smooth is more challenging than keeping smooth shifts with an MT
 
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