Reverse grinding---To service manual spec

[PAvector]

Have a 2009 Venture GT that is adjusted to the service manaual. Adjusted it before a trip because of grinding. During the trip when in reverse it got stuck between forward and reverse several times and when it did go into reverse, it went backwards in short distances but started grinding the longer I backed up. Any thoughts before I take the chain case apart. Is there a service bulletin for this model sled that addresses this. I wonder if the bottom sprocket bolt is backing out...not sure if that would affect my situation.