Hi, I need some ideas.. some fresh eyes. I have a 1991 Ford F-250. I had it in dry heated storage for a year, went and got it runs great drove great for about 100 miles. Then as i was pulling in my drivewal all 4 forward gears started slipping. Reverse is still great and hooks up just fine. Fluid smells good an there is no metal flakes in the fluid the magnet is clean... I need some ideas to check because the way it felt the tranny is good (Ithink) and not waste my money on a new tranny. Thanks for looking I NEED HELP...

 

You could have a bad Manual Lever Position Sensor.