differential lock stuck

I was offroad moving a trailer with my truck and switched on the differential lock and now it won't unlock.this truck has been sitting for a couple of years.I have not jacked up the truck to see if it was for sure locked but when i back up on uneven ground i can tell it is still locked in.

any ideas?
it's a 97 freightliner single axle,eaton rear

 

Unhook the airline and dump some air gun oil down it. Or tap it with a hammer...LOL

 

Get the hammer....lol

I'll try the lube first,thanks

 

You mentioned the truck had been setting for a while, the problem may be as Les2 is alluding to, the air cylinder gummed up, not letting the diff lock release.

 

Fixed thanks les.

 

Well, what worked?

Your Welcome

 

Note to drivers: Carry the "universal tool"...

 

There is a pipe plug where you can access the the back side of the piston and i jacked up the truck and took a screwdriver and pushed the piston back and forth while rocking the wheels by hand.

 

Good deal! Glad you got that taken care of. Did you get it working right?

 

yes i did.propably had surface rust on the piston.

thanks again.