99 tahoe starter problems

:banghead: I have a 99 tahoe and the starter has gone bad. I am on my sixth starter. I bought 5 from murrys automotive and 3 were bad and 2 went bad. I had to american somethings for 109.00 then two Bosch for 129.00. I took then back then went to Advance auto to get a Paladium starter which seemed to work until yesterday. I have checked clearance, and the voltage on the purple wire on the solenoid. I can see the starter pop out and try to engage. this is what happend to the other starters when they went bad. I have a code alarm remote starter which i have had checked it seems to be working fine. there is nothing wrong with my fly wheel. tommorrow i plan to check my altenator and ignition switch. something is causing these starters to go bad does any one have any idea what that might be.