Early this summer I managed to remove the doors on my '86 trans am and replace the hinge pins and bushings.
Now the doors are finally aligned and they close just fine, without dragging on the ground effects.

However, the driver side door still makes a "popping" sound just before the door is opened completely wide.
When you hear the sound, the door moves vertically (I think) a couple of millimeters.
This is exactly what the doors did on a larger scale when the bushings were broken.
What causes this? I can't seem to locate the problem but I'm not sure there's anything that should be done either way, since the door functions properly so far.
The passenger side door opens up perfectly smoothly with no problems like this.
Is it the spring? Or is the hinge itself just so worn out?

 

Sounds like the roller is worn out.

 

Is it difficult to replace the roller pin?

And will it do any damage to the hinges and the new pin + bushing if I insist on using the worn out roller pin?
I won't have the time to replace it until next summer.

 

The worn out roller will not do damage to the door pins but it can snap off the roller pin if not addressed. You need to remove he spring and take out the roller pin. I dont know if there is over sized pins if the knurling has worn out the door hinge. It shouldn't be to bad to remove the old pin. There may be betters rollers than this but just for example

http://www.ebay.com/itm/82-92-Camaro-Firebird-Lower-Door-Hinge-Roller-Kit-/360710234613?pt=Motors_Car_Truck_Parts_Accessories&hash=item53fc0161f5&vxp=mtr