Banshee99

Hello everyone, needing a little help here! I own a 98 z28 and she is running great! It has 178,000 and just lately it is having trouble starting. At first I thought my battery was going out. So I got it tested and it was weak so I got a new one. If I turn the key to on, then off the. Back to on and then start it will start fine but now it turns over slow and cranks over and cranks and then starts and it is puzzling, do starters ware out or go out. I thought it was rule pump but she runs great. What could be going wrong.