P0731??? stuck in possible 2nd gear??? 62TE
 

So we had a garage to install a transmission and it wont shift out of what i believe is 2nd gear. When you start out it seems like it shifts into 2nd, it will go up to about 40 but will not shift. So i thought wtf its just a bad trans because p0731 keeps showing up, so we ordered yet another trans and had it put in by another garage but only to do the same thing!. So at this point im doubting its a bad transmission. We have put in new speed sensors from autozone and it still wont do anything but what it has done. Its now been almost 3 months of trying to figure this van out. We are stumped and no one seems to have any idea around here, thats why im hoping someone on here has. ty for your time