this is a long shot try this remove pan drain fluid change filter go to parts house or order a recondition valve body.go to
www.sonnax.com bottom page order valve body dvd and order valve bodywith mod.it trys to go in reverse leads me to beleive the main gear train my be ok the valve for reverse is stuck or electric coil is burnt out.700r4 is all electric seloniod control.you have nothing to loose my get away with it you be supprise i have done wild shots my self over the years and got away with it.good luck try it.