Cadillac Repair: wont start, flex plate, one of two things

Question
i have a 2000 escalade it will not start so i bought a new starter and battery but when i turn the key all i get is a single pinging sound by where the starter is and it doesnt even try to turn over i cant figure out what the problem is

Answer
Mac,
Sounds like the starter drive is hitting something (most likely the flex-plate), but not spinning. Hate to say it but that generally means one of two things:
1. Bad starter drive
2. Seized engine
Try to see if you can rotate the engine manually.