Speedometer erratic transmission shifting erratic

Hi,
Already replaced output & input VSS and transmission shift solenoid. I'm new to the forum and am trying to tackle a puzzling issue. A little while ago (about 2 months) the speedometer started jumping around a little when I accelerated from a stop. As time passed the issue got worse until the engine light came on with P0700, P0720, P0735 trouble codes, and the transmission went into "limp mode". I did some digging and the output or input speed sensors were identified as possible culprits. I replaced both, but no change. After some more digging, I replaced the transmission control solenoid, but still the same thing. I'm running gout of lower cost options as to what might be the cause of the issue. I've tested the battery and alternator and both are good. Any other ideas.
Thx.