1992 Dodge Daytona Transmission drops out of gear

When driving, whether at highway, or street speed the trans will arbitrarily drop out of gear (appears to go to nuetral). If I pull over and shut the car off, wait about a minute or so then restart the trans will engage and shift normally for about a couple of miles or so and then repeat. Nothing other untoward seems to be going on. The fluid is clean, no outward appearing leaks. Speedometer works fine, except for when it drops out of gear, though the odometer has not been operational for a few years (the mileage I listed is a best guess). Any help would be appreciated and thanks for your time.