P1870 GMC -

Question

I have 2000 chevy blazer with p1870 code. Old trans ran hot about 230. Replaced all the solenoids and fluid. Ran trans and when temp hit about 173 degrees on scanner trans would shift hard from 1st to 2nd and the would not lock up in 4th. Had it checked and torque converter was said to be bad. Decided to replace trans and converter with gm rebuild. Installed new trans. Flushed cooler and lines. Fluid never did look bad or have much material in it. As soon as new trans hit 170 degrees started to do the same thing and code popped up. 2000 models were suppose to have ground problem fixed for board. What should be done next.