Quote:
Originally Posted by Anthony235
Perhaps low rpm bucking.
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That's what I'm wondering. He's experiencing the issue on on/off gear throttle applications at near idle and below 2,000rpms. Those are pretty low operating rpms for a 3 liter motor when it's off-boost. I know these are powerful motors, but they lack the torque when off boost and are in a tall gear at low rpms. If don't downshift and simply keep adding gas, you start spooling the turbo and may put the motor into a dangerous high load, low rpm situation. Depending on conditions (cold/hot/muggy conditions or heat soaked motor), inducing a high load, low rpm situation can cause a big boost spike and the DME (ECU) may yank timing or abruptly kill boost to keep the motor from destructing from detonation. Automatics will "unlock" and slip the torque converter to compensate for the lack of torque or will downshift to keep from inducing a high load, low rpm situation.
I can feel a very minor drivetrain thud when letting off the throttle while in gear in 6th on the highway (rpms 2000-2500 or so) and I can feel something similar through the seat when I'm in a tall gear and running at a low rpms (i.e., below 2,000rpm). I notice it more now than I did when I first got the car, but I believe it's because I'm paying more attention to things after 7 months and 7K miles of ownership. I also understand that things have loosen up a bit in the drivetrain.
I can't say this sensation/thud isn't uncommon to me though. My 2012 WRX 5MT did it, my 1996 Maxima 5MT did it, and all my prior manual Hondas did it. Some worse than others. What I felt was just the nature of operating a manual transmission at low rpms, the engine lacking some initial torque to overcome the load, and the drivetrain rocking a bit in its soft motor mounts.