Hi! my name is XXXXX XXXXX I can help. Sounds like your transmission is okay in first gear, and when it comes time to 2nd, just goes into neutral. Correct me if I am wrong. This is not a shift solenoid, or valve body, because if it was, would just stay in 1st gear, without the "neutral" feeling, just rpms will raise with engine
speed. There is an internal pressure leak in your transmission, and will be a bad intermediate clutch/ piston seal. The transmission must be removed, disasembled to repair. No way around it. Since the fluid still looks good, recommend contacting local shops, transmission shops and explain your situation. Will be much cheaper and more reliable to have your transmission removed and rebuilt, instead of buying a used/ reman transmission. The fact that your fluid looks good means your valve body, torque converter, and pump will not be contaminated, so the shop should not recommend these expensive parts, if so, recommend a new shop.
Thanks, XXXXX XXXXX this may not be the answer you are hoping for, it is correct, and an accept is greatly appreciated.
Will be here to answer any more questions regarding this problem regardless of accept status.