You can "manually " shift a stock trans but it is programmed to shift up at a set point regardless of where the lever is and will not downshift above a certain point when the shifter is pulled back.A shift kit lets you lock a gear in until the engine blows.
Mine has full engine braking on the downshifts;great for nice twisty downhill runs, use the engine to slow for the corners not the brakes

 

The limit you are referring was so far on my old stock trans.
If I was in 2 (with the lever in 2) and doing a WOT, It will not upshift in third until 6500 or over (well over the limit of the valvetrain).
If with the lever in 3 (or D) at 70 mph, moving the lever to 2 it was used to downshift.
If I was in the same situation (with the lever in D) and at 100 mph, the last think that my mind was thinking was to downshift to 2. So if the Shift kit (Transgo or the Art Carr you have) allow this, this is not a "plus".
My old stock trans was with engine brake.
I'm not here to say that your kit (and mine -I have a Trango Shift kit on my actual trans installed by Pete K- ) is not good. I want only to say that the advantages of these kits are more evident on NON-corvette car.
The advantages on corvette are (IMO) that the shifts are much more faster than the stock, downshifts are very quick, and the upshifts are more firm.
The "manual control on 1 and 2" and the automatic function on D you are referring, are advertised more for nON-corvette trans owners.

A "real" manual control (for me) is when you can move the lever at WOT (or near WOT) at -say3500 rpm- and the upshift occurs.
(I said 3500 because it's a rpm level where the governor can't command an upshift on automatic operations).

The Trans of my dreams is like this:
1-2-3 with TOTAL manual control (as explained above), where if you let the lever in 3 and you approch to a stop it will not automatically downshift to 2 and then to 1 when completely stopped. (the same Sliding has and the same I had),.... but with the addition of the
4 (OD) with total automatic features.
with lever in 1 it will stay in 1 on all speeds, all rpms, all gas pedal %
with lever in 2 it will stay in 2 on all speeds, all rpms, all gas pedal %.
with lever in 3 it will stay in 3 on all speeds, all rpms, all gas pedal %.
...
with lever in 4 it's an automatic trans where it selects the right gear depending on speed, rpm and gas pedal %.

I don't think is possible to have a trans like this.
-Beppe-

 

hmm good food for thought

 

"The "manual control on 1 and 2" and the automatic function on D you are referring, are advertised more for NON-corvette trans owners."

Point taken ; I used a cheaper non Vette trans for my performance build so I needed the upgrade.
Maybe Pete could design the trans of your "dreams"

 

Not, he said he can't because it's impossible.

Impossible for Pete???


-Beppe-