You are definitely better off to error towards a 2-3 shift flare than a bind.

While the flare (slipping) will wear out/ burn friction material...
Binding (especially on a severe 2-3 shift bind-up) can cause hard parts failure.

I would always be happier to have to rebuild a unit over worn-out/ burnt clutches and the mess it leaves in the pan...
Compared to the big mess (metal-debris) and broken hard-parts that have to be replaced.

The 2-3 shift on a performance application (especially when I build these for 600 to 1,200 HP) is very critical and takes quite a bit of hydraulic calibration to get correct.
After everything tests correctly on the Transmission Run-Stand/ Dyno...
I test the unit in the car for the 2-3 shift on road tests.

Often I will have to drop the valve-body and change 1 to 3 orifice holes in the separator plate.
Below are simplified fluid diagrams.
The first image is the hydraulic diagram for the 2-3 shift stock, and then the second image is how I modify these circuits:




After I modify the valve-body and separator plate, the diagram looks like this:



The second image shows how I make direct paths (fluid passages) to the 2-4 Band and 3-4 Clutch.
I do this by:

-Blocking the 3-2 Control Valve into the closed position with a small spring inboard of the valve (omitting the original spring).
-Omitting the #2 Check-Ball and separator-plate hole.
-Enlarge the Letter G orifice next to the #2 Check-Ball to a calculated size.
-Omitting the #4 Check-Ball and separator-plate hole.
-Enlarge the Letter C orifice next to the #4 Check-Ball to a calculated size.
-Enlarge the Letter A orifice to a calculated size.

There are multiple factors that dictate the sizes of the 3 orifices (G, C, and A).
These 3 separator-plate holes often have to be resized a few times once I road test the vehicle.
I will have to drop the valve-body once or twice to get the 2-3 shift perfect.
These 3 separator-plate holes give me complete control over the 2-3 shift to prevent a Flare or Bind.

You have never experienced a 2-3 shift like this before if your valve-body is not configured this way!
Yes there are other ways to make it work...
But nothing like this!
Especially with one of the 4L79E Input-Drums!!!
It is a completely different transmission in terms of the 2-3 shift (you would never know it was a synchronized shift).

 

Your diagram makes it pretty clear that the key to timing 2nd servo release to 3-4 clutch apply is hole G. Your revision to the 3-2 shift valve circuits is pretty similar in effect to the Transgo 2-3 shift kit mods to that same circuit. I did up size hole G my last time through. I had been running the Superior 2nd servo with more apply area than the Sonnax. I switched to the Sonnax and installed the heavier return spring. I could easily take hole G out a bit more. That would speed up the 2nd servo release.

I have all the changes I've made cataloged, largely in threads here and on the Hotrodders forum. I need to go back and refresh my memory. I also need to start keeping better notes as well as drawing out diagrams when I make changes. It sucks trying to remember some of the design changes I make two or three years later.

 

Yes.

When GM designed the 3-2 Control valve for the THM200-4R...
On paper the valve was supposed to operate as an ON/ OFF switch to control the rate of the 3-2 down-shift.

In reality... the 3-2 Control valve operates as a BIG variable orifice.
Governor pressure is constantly moving the 3-2 Control valve into different positions (allowing different amounts of 3rd Accumulator fluid past the valve).
This creates an undesirable result of inconsistent shift timing for the 2-3 and 3-2 shifts.

By blocking off/ closing the 3-2 control valve all the time...
We can control the 2-3 and 3-2 shift timing via the orifice at #44/ G.

Hole "C" is for 3rd exhaust.
Hole "A" is for 3rd feed.

All three of these holes are important and are in relation to one another for shift timing.
I do not recommend omitting the #2 or #4 check-***** unless you are prepared to possibly tweak the holes sizes a few times with road testing.

 

I haven't gone back and studied the circuits yet. Check ball #2 comes out and the hole is blocked in the TG 2-3 shift kit. That part of your mods is already done. I remember the last time I was looking at this, when I switched from the Superior servo to the Sonnax, Dana told me to upsize hole G and I did but I don't know if I went as large as he said to. If that was a mistake, that's on me for not listening. I installed the heavier return spring but you know at high line pressure, the added spring is a small change compared to the force of the hydraulics. I could very easily trim hole G just one drill size (1/64"). As well as it's shifting though, I may just wait until I'm ready to upgrade the 3-4 clutch to 9 frictions.

I don't know about check ball #4. I'll look into that. I know the TG kit deletes all but 2 VB check *****. Today was the first time I actually did a hard throttle run from standing start to 70mph, through the 2-3 shift. It felt real good. It may be a hair too quick, but it is a tiny difference. At hard throttle, the 2-3 shift feels just like the 1-2 shift, it plants you in the seat. At light throttle it feels a hair tighter. But then I also have to take into account that at light throttle around town, when I do the 2-3 shift, I'm easing off the throttle and some of what I feel is engine braking. My trans won't do the 2-3 shift below 35mph.