96 Ranger Auto Transmission Problem

My brothers 96 Ranger Transmission is acting up. When cold, if the transmission is shifted into reverse, the car doesnt move, and it pulses putting a big load on the engine. Once put back into park, the engine idles normally, and the "O/D OFF" light flashes. Does anymody know what this means? Can codes be read from a 96 without a scan tool? I have access to an oscilloscope, so I can make all kinds of measurements.

I have a 1997 Ranger 4.0 6 cylinder with 211,000 miles never had any trouble until now with the transmission my overdrive light started blinking ,shop informed me that once it blinks it is senceing problems,it will cause it to heat up, not showing on dash, and cause other parts to go bad. my torque converter was out ,sensors out, no 4th gear. had it overhauled.hope problem goes away. truck had never had any major problems, except for normal problems, tune up, brakes, barttery etc. hope my next one in the future performs like this one.