1999 Ford Ranger Start 99 3 0 Put Into Reverse Down Drive Way Ther Truck Will Tp

so when i start my ford ranger 99 3.0 and i put it into reverse to go down my drive way ther truck will go in then when i go tp put it in drive it can be shifted into d but it wont move i oush the gas it revs up and wont move then if u waite a min it kicks back into drive so u can move then it falls out agen it stops and drive fine and goes into gear fine when it warms up a little bit i checked the trany fluid level and added transmision slip stuff nothing still does it till the truck warms up