why will my truck not shift into gear? on 1990 Isuzu Pickup

My clutch feels fine it has pressure when you push it to the floor, and it feels like it is shifting through the gears but when i try to drive nothing happens almost like it is stuck in nuetral why wont it take off?

Asked by for the 1990 Isuzu Pickup
Either the clutch has failed because the friction plates have disintegrated from wearing thin, or the center of the clutch disc has fractured. If the clutch hasn't actually failed, then an axle shaft or the differential gears have broken and failed. Those are my first two guesses. It'd be interesting to have the truck running in gear (of course the vehicle is motionless with the brake on) and look under the vehicle to see if the driveshaft is turning or not. If so, then the differential or an axle shaft has failed. If not, then the clutch or gearbox has failed.
I think if the driveshaft is spinning, it's not unlikely that an axle spline has stripped, now that I think of it.
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