No forward gears, only reverse

Car listed above is an model with a140e transmission, 4 speed. Car will engage and move in reverse, but no forward gears. Car had small drivers side axle seal leak and was driven on a long road trip before it shut off. May have been 1 quart low ATF before it shut off. No check engine lights, and transmission pan filter replaced approximately 7 months ago. Since purchased have done 3 drain and fills with Walmart Dexron III fluid. I am a hobby mechanic and have done about $2,000.00 of replacement parts on the car. Want to make sure the transmission is bad before I decide what to do. Thanks