My Ford f150 1998 truck it has two hundred thousand miles it has locked up on me It has done this one time before but this time it has not unlocked I thought it was a transmission but it seems not to be I don't know if it the breaks it cranked when it did move i don't know if that has anything to do ok it will turn on but even if i put it in neutral the back tires won't move.

 

Does the motor crank?
Does the motor start?
Does the vehicle roll while in neutral (even when not started but if you push it).

You didnt really give any definition of 'stuck'.

Please clarify what is truly happening, somebody here may be able to help (I won't, but your post is missing important stuff).

 

It turns on but it will not move even if its in neutral i have tried to push it the motor does crank

 

What was happening when it locked up? While driving? Or? Rear-end locked up? Has the rear-end ever been serviced?

 

You never define what locked up.

Engine, transmission, rear end?

 

Very vague explanation.You have to determine what is seized.
Engine- Does the engine crank? Hard to tell if the engine runs from your explanation.Use a breaker bar on the crankshaft bolt and try to rotate.If the engine rotates but does not crank, you have to troubleshoot the battery/ starting system.
Brakes- safely raise rear end, put in neutral and try to rotate wheels. You can go one step further by disconnecting the drive shaft to see if the differential is seized.
Transmission- if the engine and differential rotate but the drive shaft doesn't, the transmission or maybe the carrier bearing is seized.

Maybe you might have more responses by posting in the appropriate forum (1997-2003) for your 1998 truck.