I built my 4l60e trans and its well known that if he input drum assembly leaks on the shaft area where it goes into the drum. There are many up dates for the p1870code. it causes many issues with he trans and converter.If the valvebody isn't updated it will slip and burn up the 3-4 and converter. do u have any low gears at all?

 

if you have no gears at all, that would be your pump.