Shift linkages not put in the correct spots.
What would cause the 1995 Nissan Pathfinder not to go in forward or reverse?
If no forward or slipping forward suspect problem in the forward clutch and circuit. Reverse does not use the same applied components
Assuming automatic transmission, brake bands need adjustment/replacement
If this is an automatic transmission, more than likely the transmission is on it's way to the junkyard. Usually failing transmissions lose reverse first, then the higher forward gears - last will be the lowest forward gears.
the letter d
Having it on "PARKING"
The tranny is broke.
Most likely your transmission needs replaced.
Check transmission Fluids.
Weight of the vehicle
Tranny is going out
The transmission is broken. Take it to a shop.