front differential lower mount bolts
 

Background:
I recently purchased a 2008 Escalade. During several test drives, I noticed no unusual sounds. After we bought it and drove it for a while I noticed and felt a clunk in the front end when I accelerated to 35-45 MPH, let off the gas and then reapplied the throttle. When I hit the throttle the clunk occurs.

I had a friend who is a GM mechanic drive the car and check it out. He found the two bolts on the driver side front differential mount are missing. He said, "They are the ones that go in a verticle direction". We power braked the car in reverse and then drive while he looked under the car. He said he could see the differential lift off the mount.

He thinks someone worked on the differential and didn't tighten the bolts or left them off. The CARFAX shows the differential was "serviced at 51,000 miles. The vehicle currently has 81,000 miles on it.

Questions:
1. Anyone ever see this failure mode?
2. I have looked online for the bolt part number and can't find anything. Can anyone help me out on that?