1994 e-150 shifting problems

have a 1994 e-150 with a AODE/W auto tranny it will go in gear fine and shift into 2nd gear fine then stays there and wont shift in 3rd,plus it goes in reverse no problem,nothing slips it just wont shift past 2nd gear.any ideas thanks. update,i took the pan off and the fluid was veery dark almost black plus,the bottom of the pan had a black residue on it but there was no chips or shavings,the filter was dark red on the inside caude that be why its not shifting into 3rd and overdrive and one more thing the o/d light on the shifter keeps blinking