* Worn or damaged shift linkage: This is the most likely culprit. Over time, the linkage components can wear, become loose, or even break, allowing the transmission to shift unintentionally.
* Transmission problems: Internal transmission problems, such as worn synchronizers or a failing shift mechanism within the transmission itself, could cause the transmission to disengage from first gear. This is a more serious issue.
* Improper parking: If the parking brake isn't fully engaged, the vehicle might roll slightly, causing enough stress on the transmission to shift out of gear. This is especially true on inclines.
* Damaged or improperly adjusted clutch (manual transmission): If it's a manual transmission, a worn or improperly adjusted clutch could contribute to the problem.
* Damaged transmission mounts: Worn or broken motor mounts or transmission mounts could allow excessive vibration, potentially causing the transmission to shift.
In short, while not a common occurrence, several mechanical issues could cause a 1995 Ford Explorer to pop out of gear even when parked in first. It's a strong indicator of a significant problem that needs professional attention from a mechanic to diagnose and repair. Driving a vehicle with this issue is unsafe.
