Loss of all gears with an automatic transaxle

Loss of all gears with an automatic transaxle
I got the car when my mom passed in 03 with right under 40 thousand original miles the motor is sound it has an automatic 3 speed transaxle and ever so often when starting out it would want to slip into the next gear and shift fine after that, then one morning it did just that then I lost all gears no reverse, first, second or third I've been tolled that it striped a spline and would need rebuilding, is there anything else it could be or that I might check before making the move to rebuild it?