4L60E Reverse and 1st Only after Transgo HD2 Kit

Question

I have a 1999 4L60E from a 1999 Suburban that has been rebuilt twice successfully, and then had a TransGo 4L60E-HD2 shift kit installed that ultimately led to where it's at now with it's reverse and 1st only issue. I've been through quite a bit of troubleshooting and am basically at a loss

Speedometer is working correctly
Both shift solenoids have a resistance of 25 Ohms and click nicely with a 9v battery
If my transmission control/PCM is unplugged completely it limps still in
1st gear (which to my understanding is supposed to be impossible, since both solenoids being off should be 3rd)
You can kind of feel the transmission try to shift to 2nd barely when it's supposed to, and then stops "trying"
Commanding gears with the trans controller doesn't change anything
Using the gear selector/tree also doesn't get out of 1st/R
Sonnax Corvette servo installed with just enough shims to allow the input shaft to still be hand-rotatable
Nothing I've torn down so far has any wear, and there's been no odd noises coming from anywhere while driving
TPS shows correctly in my transmission controller software, reading from about .5v to 3.4v

Based on what I can find out by other forums and such, this collection of symptoms seems to be a very uncommon one. It was working 100% before the shift kit install, which only had us replace parts in the valve body, but it was never able to shift out of first since.
I currently have the transmission out with the valve body partially disassembled. What should I be testing?

Brian Leishman · Answer

Found out what was wrong! It was my stupidity, unfortunately, but that's the goal I suppose, is to make mistakes and learn.
So the problem was, that while installing we broke off the top of the 3-2 downshift solenoid, and ended up needing to replace it. Somewhere in the middle of that, we left out the 3-2 control valve and spring completely. Luckily when tearing it down we noticed that as the issue, found the parts, reinstalled, and everything worked wonderfully!

The rest of the shift kit instructions were followed to the letter, including flipping all the valve body pistons upside and whatnot, and it's working great.

4L60E Reverse and 1st Only after Transgo HD2 Kit

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