my 77 pinto drives fine and shifts like a dream, but when it warms up , say 20 minutes of driving, i cant put it in any gear at all, unless i turn the car off and put it in the gear i want, if im moving i can shift, its only at 5mph or stopped when i cant shift, transmission gear oil is fine, clutch doesnt make any noise, no bad noises at all, im thinking it has somthing to do with the clutch, but it feels good, sombody with help please!