Likely the Intermediate Steering Shaft. There is a TSB on that.

 

ok got it back today after they replaced the I-Shaft and while i was backing out of the parking spot its still knocking! made a u turn in the parking lot it pops about 10 more times, so i go back in get the Tech and he takes a ride with me and hears it so now its back out there and their trying to figure out what it is. so 3 days and still no car, no rental car either