I replaced the hinges on my 98. so worth it. just a little $$$... but swings like a million bucks... I tried greasing it every way i could think of and fit grease in there. there is a point where its just not saveable.
What have we got?
We have one heavily armed Recreational Vehicle
I just sprayed some penetrating oil into them and worked them back and forth, and then sprayed them again, and kept working the tailgate back and forth. That freed them up quite nicely, and then to protect them a little from getting bad again too fast, I sprayed on some white lithium grease and worked it in a little. Took about 5 minutes and they swing like new!
i've been spraying wd-40 on them and swinging back and forth for an hour with no improvement.
No matter how much the WD-40 marketing team wants you to believe it, WD-40 is NOT A LUBRICANT. It will actually strip lubricants OUT of what it hits. It's primary purpose is to prevent rust, and to help break it free if it has already taken hold.
You want to be using a penetrating oil at all the hinge gaps. Or, as you mentioned, drilling a small hole and forcing some oil/grease into it. Careful not to go too far in and mess up the pin though.
Slick 50 makes a spray lube in a red can, the stuff is amazing, I use it on everything, hard to find, I have had my can for 8 years now, hope It never runs out. It has solved problems no other lubes have.
Copy on the WD 40. It's old school and does not lube, prevents rust