My o4 mountaineer premier idk if its my front differential because I could shake a good inch with my hands or the transmission but it don't matter the gear I'm in its like its stuck in neutral it just tacs up and won't go anywhere but you can feel it shift into gear but still won't move

SOURCE: 1996 Dodge Ram Transmission shifting problem

I had the same problem with my 96 Ram 1500. I thought I was going to have to pull it out and get it rebuilt or just replace it. That was at 134,000Km it's now got 210,000 and shifting like a dream. What I did to solve the problem was this, as follows:
1. No lucas transmission Fix makes things worse.
2. Get your self a new transmission filter and gasket
3. Grab Gunk transmission medic 12oz
4. Grab 7 Liters of Valvoline ATF+4 transmission fluid (Made for chrysler transmissions)
5. Drop the trans pan and drain all the oil, clean pan and magnet
6. start truck for 5 seconds and the pump will pour out another 1 liter
7. re-install filter, gasket and pan, then add your Valvoline ATF+4
8. Add, the valvoline, transmission medic and make sure you have the right level of fluid

That solved my transmission problems, instantly it was shifting better, I no longer had to let off the gas to make it shift. Now if you have large pieces of metal on the magnet, and it's totally covered in filings, you might want to consider rebuilding the trans. My magnet had usual clutch.         

Anyhow good luck, let me know if it did the trick for you.
Justin

SOURCE: My 2003 Mercury Mountaineer Gear Shift is stuck.

See if u have brake lights. This is what energizes the shifter solenoid. There are 2 fuses u can check both are in the under dash fuse panel. Fuse 23 (15amp) and fuse 26 (7.5amp).
To get it out of park turn igntion switch on stopping just short of engerizing the electronics then u should be able to get it out of park and into neutral.

SOURCE: My 2003 Mercury Mountaineer Gear Shift is stuck.

THERE IS A SENSOR ON THE BRAKE PEDAL THAT RELEASES THE THE SHIFTER.THERE A 3 COMPONENTS INVOLVED.U CAN PUT IT IN NEUTRAL BEFORE U START THE CAR.THEN WIL SHIFT.

SOURCE: gear shift stuck in neutral when moving to park

1st check your shifter linkage-does the indication coincide with your gear recognition display in instrument cluster? most liley if it is not the linkage the gear recognition swith inside your shift box is defective-usually they get soda or coffee spelled on them and malfution. I would recomend having you car scanned for codes.

SOURCE: My 2005 buick rainier is stuck in park.

if the car is on a steep incline could prevent it from engaging