Thank you for your reply. But what you're referring to are common 6hp issues. Bridge and seals not sealing properly causing pressure loss are very common on 6hp transmissions I was inside few of them but 8HP doesn't have these seals.
My question is if it's even worth the shot to try rebuild valvebody + solenoids as the cost would be nearly same as used transmission. But if I could avoid to pull this big boy out I would definitely prefer that.