370z Auto - High-RPM acceleration issue w/ 3.7 gears

jmikes

Was curious if anyone here has any idea what might be going on.

For my auto 370z I did a differential swap with a manual 370z sport diff which put me from the stock auto 3.3 final drive to the stock manual 3.69 final drive. Ever since then, my car now has some form of hang-up or power loss after 7200 RPM that wasn't there before the differential swap.

It's most noticeable when flooring it from a standstill in auto mode. In auto mode with the ~7500 shift point, there's a slight but noticeable loss of acceleration for the fraction of a second between 7200 and 7500 RPM and it takes longer than normal to rev up through that range.

With using GPS-based "drag apps" on my phone, with my current set up in Auto mode I consistently get 4.8-5.0 second 0-60 times, while if I use manual mode and manually shift at 7200 I drop all the way down to 4.2-4.4 seconds. (I'm aware that Phone GPS-based drag apps aren't exactly accurate, but this is dozens of 0-60 pulls in auto and manual mode that all consistently hit the same, and they line up with the feeling of power loss at 7200+.)

This occurs both with a stock tune and my custom tunes.

Is this something I will need to use a dyno for, or is there some very odd or badly labeled setting that is the key to fixing it? I'm just not sure what it could be at this point or why swapping a diff would cause it.

I use HPTuners if anyone's got experience with it and might know how to fix it with tuning.

Thanks guys.