I own a TSX but I think transmission issue could fit in here. I'm getting gear lock out at high RPM's , mainly in red line. I estimate a full second of lockout and that is a huge "power loss." I've read that it could be worn motor mounts so I installed a torque damper and nothing was improved.

My next "fix" would be replacing clutch master cylinder and slave cylinder. Would changing those fix it? What could be the problem with gears locking out at high RPM.

 

I will assume manual (sorry dodn;t read the last sentence with replacing the CMC and slave) and it could likely be the Clutch Delay Valve.
It is a PITA on my S2000.

 

From a post on Evolutionm.

"Now about lock out. Lock out occurs when there isn't enough air gap between the disc pressure plate and the flywheel to allow the clutch to disengage at high rpm. The reason the above occurs are as follows: bent disc (hanging the transmission off the input shaft - install error, warped pressure plate, or flywheel - excessive heat - driver error as a result of slipping the clutch too much and a mis-adjusted or not even adjusted clutch - user/installer error."

You can also try adjusting the clutch pedal to see if this helps if yours engages close to the floor.
https://acurazine.com/forums/1g-tsx-problems-fixes-128/solved-clutch-pedal-low-engagement-point-837892/

 

How's the quality of shifting at lower RPMS? Any grinding / notchy feeling going through gears?

 

I read that post too. Definitely not any install error since I'm on OEM clutch. I'm guessing my pressure plate or flywheel is warped but I don't even drive that aggressively. Granted I am almost at 90k miles.

Shifting in lower RPM's has not changed since I got the car (Or at least as far as I can remember). I don't experience any grind and it's smooth and every gear. Although I do have a hard time quick shifting even at lower RPM's. Not sure when this started happening or is it normal in an Acura?