I am getting close to the end of the mileage warranty. Does the power train warranty last up to 5 years? Would removing the DPF void the powertrain warranty?
I would like to go with a new exhaust asap.

5 years OR 100,000 miles, whichever comes first. If before these two criterias are met, you tune/remove exhaust, yes, your Powertrain warranty is probably going to have problems. Chris

And just one more thing, your sig shows a 2008 Silverado LBZ you have LMM if '08.