1995g20 van code 42 wont shift out of 1

Hi, First, the TH400 is not electronically controlled; the transmission your van came with, the 4L60-E, is electronically controlled. Plus, the TH400 is a 3-speed and the 4L60-E is a 4-speed. So, the two transmissions are completely different and swapping them could breed a lot of issues. Secondly, as you know, code 42 is for the ignition control circuit. And, because sometimes engine performance problems can mimic transmission concerns, you may want to address the code first. I see you've already tried a lot of common fixes to cure the code (ignition module, coil, etc.) and the problem remains. I'm guessing you also checked that the "set timing connector" is intact? If not, check that out. At this point, you've thrown a lot of parts at the van, including a transmission. I recommend having a professional diagnose the problem firsthand to avoid further unnecessary parts replacement. You can find recommended repair shops in your area here: https://repairpal.com/repair-shops

The TH400 should shift just fine provided there is a sufficient vacuum supply to the modulator valve and wiring to the detent (kick down) solenoid is correct. Now this doesn’t imply it will function properly otherwise in this particular vehicle but shifting out of low gear should certainly occur!