I’m going to throw together a backup trans tomorrow. Reid case and old non-pro brake valvebody. Last time it this case/valvebody was used, the high gear activation was delayed. Like .2 to .3 longer than a different good trans. Activation is decently firm just happens a long time after the shifter handle moves.

The car I’m putting it in now shifts on time so not that hard to account for the delay, just curious if there is something I should look for when I put it back together.

Clutches and everything looked good when I took it apart.

The one time we saw something similar I'm 99% sure it was related to the check ball in the high gear drum.

The shift lever is keyed/splined through the rooster comb. Slop due to an undersized/chinese manufactured shift lever or cracked rooster could cause a late shift.

Best case scenario is an interference fit so to speak between the lever and comb. No slop without the pinch bolt snug.

Look at the spring behind the servo piston. See if it is aftermarket and stiffer than a stock spring. It is a balance between the spring and the fluid pressure from the opposite side of the piston that times the shift. The fact that the clutches look good would suggest this is not a problem but I would check anyway.