Sometimes when i put in rverse to back out of my garage the car does not engage.

What is your question?

Does not do all the time but is getting worse. When I hit the gas after it does not engage, it will all of a sudden engage and jump with noise. Could you advise what it could be and how to fix. Also during the recall concerning the key switch also had the shifter recall replaced.

What makes this problem better or worse?

Nothing

How long has your 2006 Chevrolet HHR had this problem?

Off and on for about 6 months