Is it a problem to take hydrocodone that is 3 years expired?

Unreliable potency: The primary problem of expired meds is their unreliable level of potency. It is unlikely that it would be excessively strong if in pill form, though i've seen that problem in liquids. It would be prudent to ask your pcp for an update if needed & drop the expired med by a pharmacy where they can dispose of it safely (& thru state & fed regs).