I have all gears but reverse and when in park and neutral and gas pedal is pressed the car moves forward, why?

Go see if your cable has become disconnected/broken leaving you in neutral.

P=park gear position (no gear selected)
R=reverse gear position
N=neutral gear position (no gear selected)
D=top gear
2=fixed highest gear (used for speed when climbing an average incline and to control speed on decent)
1=fixed lowest gear (used for climbing steep incline or descending slowly)
Note-: Never engage Reverse gear when traveling forwards and never put into Park when moving forward or backwards, also towing most autos should be done no more than 10mph, fast towing can damage the gearbox, also make sure gear is in Neutral when towing.

Transmission may now be toast since you continued to drive it when maybe low on fluid or torque converter had failed. How long since last fluid and filter change? Ever?

The question is a little vague but I think I know what your referring to. All modern automatic transmissions have torque converters. This is the device that connects the engine to the transmission. All vehicle manufacturers like the trans to be nice and smooth shifting. That's great but it does come with some minor drawbacks. If you are facing slightly down hill and you put your car in reverse but do not step on the gas slightly I can guarantee that you will indeed roll forward. You can eliminate that issue by holding your left foot on the brake while you shift into reverse. Then, as soon as you feel the trans engage, gently depress the gas pedal with your right foot and it will eliminate that forward roll problem.

Vehicle does not move forward.
The following parts and assemblies need to be checked thoroughly.
1. Manual valve
2. Valve body assembly
3. Forward clutch C1
4. Planetary gear unit
5. 1st and reverse brake (B3)
6. Park/ neutral position switch

Make sure you car is actually in PARK, Easy to do, Just disengage the parking brake (emergency brake) and attempt to push your car both forward and reverse to ensure your car isnt in neutral. If you cant budge the vehicle your good to go! If it rolls forward it may be in neutral or a forward gear. if it rolls backwards it may be in neutral or reverse. If it rolls both directions its in neutral. On that note if it moves at all skip to the third step (***) and make sure the transmissions shift bracket is in the park possition. Depending on your cars transmission model the parking gear is located all the way left to the farthest possition or all the way right to the farthest possition) One direction will put you in Park, the other in will put you in 1st gear, If your in 1st gear the linkage should be too far away from the shift plate to connect if your column says you are in park. DO NOT ATTEMPT TO START YOUR CAR WHILE IT IS IN A DRIVE GEAR AND THE LINKAGE IS DISCONNECTED IF YOU ARE ABLE TO START YOUR CAR IN ITS CURRENT STATE DO NOT MOVE THE TRANSMISSIONS SHIFT BRACKET UNTIL LATER IN THIS INSTRUCTIONAL!!!!!

* Floor shift automatic, the push pin lever (located inside your shifter/gear stick) may be malfunctioning. You have to pop the grip off and inspect the white plastic pin inside the shaft to see if it is damaged, also check inside the grip while you press the safety release (shift lock button) to ensure the internal slide mechanics are propperly working). Also check for anything obstructing the levers movement inside the floor housing.

** Column Shift. Make sure your pull pin lock is working properly (disengages the shift lock when you pull back the gear shift before you select a gear) if its broke theres two possible behaviors you'll experiance -1. You cant pull the gear shift back at all or -2. No effort or less than normal effot is required to pull back the gear shift. If all that checks out then you have to inspect the steering column linkage bar (you may have to remove some of the steering column housing to view it. Make sure the bar isn't bent or that its movement isnt obstructed.

***Automatic Transmission Linkage Check - Look under the kick panel located above the gas and brake pedals.........Once linkage is located under the dash (kick panel) disconnect it and try the gear shift. If the cable moves under the dash then reconnect it and move on to the next step.
Now block the wheels and climb under the car and disconnect the linkage from the transmission and have someone work the gear shift while you see if the cable is operating propperly, if the linkage moves (as it should) then try shifting the transmission back and fourth by hand while the linkage is disconnected., If the shift bracket feels stiff or is dirty clean it off with non corosive chemicals so you dont damage any seals. If the bracket operates smoother go ahead and reconnect the linkage and try shifting with the column again. Be sure to move the shift bracket back to the park position and make sure your shifter column is in park as well before you reconnect the linkage, if you dont you are sure to run into more issues.

Hope this helps you out! If all the mentioned area's above are in working order then your problem is with the car's transmission and you should take it to a speciallist.

first check the gear box oil level if its low top it up,,,,if this dont fix it you have a gear box problem

your problem lies in the internal parts of your transmission which are the clutch linings, they are already worn out and starts to slide.

shift linkage needs adjusting,,could be bent, easy fix, located along firewall to fram beneath the column, ask your son wut he ran over and didnt tell u about... hope i could help...:)

What engine? Rear wheel drive ?Sounds like shift linkage or cable out of adjustment slightly. Have a look at where cable or rod attaches to transmission for adjustment. If not sure of what your looking for get back to me with info.