I have a 7FGU25-70383. this is an electric shift transmission.REVERSE works fine. customers complaint pulls forward. and up an incline no problem then like a light switch fwd stops after about an hour of heavy use. reverse still working. into the shop it came after inspecting and thinking,the trans fld is clean no burnt fld. I replaced both shifter solenoids fwd and reverse.and harness going into valve body. red wire yellow wire. reassembled tested works for about 4 hrs. the stops pulling forward let cool down 30 min pulls forward again. any ideas.