ok so I have 2000 suburban 1500.i pull the rear tire to change pads.and the pad that set on the caplier is messed up bad.but pad on the outside look good.what could have caused this issues?it dual piston caplier are they worth rebuilding?

 

Sounds like the caliper stuck. Be sure that the pins are clean and lube them w/ caliper grease that usually comes w/ new pads.

 

I would concur, make sure the caliper is able to freely move....
Do you regularly use your parking brake?

 

I will check that along with the boots seals.no I don't use the parking brake much.

 

As far as I know regular use of the parking brake keeps the rears adjusted, and you'd be surprised at just how small the parking sprag is that holds the vehicle in place.