hey i just got a 1987 ford ranger 4x4 long bed 4spd auto with fisher plow and when i got it the guy said it was stuck in 4 lo and that's how he used it to plow (btw its manual shift with manual hubs) the shifter wouldn't budge in any gear so i put it in neutral and forced it (very hard) to go down and it shifted into 4 hi then 2wd i haven't messed with it much since then but i was able force it back up into 4 hi then back into 2wd. any ideas whats wrong with it or how to fix it?