There's one other thing you might want to consider.... this engine uses Honda's flawed Variable Cylinder Management system (VCM for short). It is aggressive and this transmission was never designed to work with it. I firmly believe that a lot of the eccentricities of this drivetrain are due to differences in torque at light throttle and/or late disengagement of the VCM system. I bought a VCM Tuner 2, which basically tricks the ECU into leaving VCM off entirely. This results in about a 1MPG drop in fuel economy, primarily on the highway. It also prevents oil burning, which has been a problem in this engine for a long time now (Honda's even been sued over it).I called the dealer where we purchased our MDX (their Acura office and service is in their Honda dealership). Going to see what they recommend because I have a huge feeling the local Acura dealer didn't do the job correctly.
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When I first installed the VCM Tuner, it largely mitigated the harshness, particularly at light throttle and made driving the car much more bearable. I uninstalled it when I went to have the dealer do the TSB. I can still feel some of the shuddering on occasion and certainly late shifts or delayed throttle response that are indicative of the VCM being enabled, but the shifting issues definitely seem to be completely mitigated, at least on my '19.
If you're not concerned with fuel economy and you like better throttle response, this might be the answer you've been seeking. I've heard more than one person on here say that it's resolved shifting issues in older models with the ZF9. It will likely prolong the life of the entire drivetrain as well. Just something to think about.
It's a helluva lot cheaper than having the dealer do a drain and fill too.... VCMTUNER II - Advanced - 2007+ for Honda Acura 3.5L I-VTEC Disable VCM / ECO mode