I have a 97 4 door 4x4. I noticed about a month ago when I would shift in and out of reverse it was a little delayed a couple of times but it was inconsistent so I thought nothing of it. This past Saturday I was trying to back out of my friends driveway and there was a crack in the driveway about a half inch tall and the Blazer just could not back up the crack at all. Drove it home and it was completely fine. Problem only occurred in reverse. Then today I was packing out of a parking space when I heard a couple of clunks when I was backing up. Again, drove home with no problems. Doesn't slip when going forward at all and my fluids are fine. Is there anyway to test this?