have the ability to buy a cheap set of snow tires from a 2011 crown vic is there any problem using them on my 2004 grand marquis??

 

IF both sets of tires are the same size, you should be good to go.
However, the 2004 Crown Vic and the 2011 Grand Marquis have different size WHEELS, so the tires may not be interchangeable.
Tire experts tell us that radial tires should not be switched from one side of the vehicle to the other side, so it would be best to mount the "new" tires on the same side of the vehicle that they were originally installed on, if possible.
Good Luck !!

Classic Style 15" -- "Italian Lace" Wheels