Bad tranny?

[Twiz]

1990 Silverado k 2500 with auto trans.

Drove my truck yesterday and she drove great. Fired her up this morning to get to work and let her warm up for about 30 mins. When I jumped in and shifted into reverse she rolled forward about 2 inches. Neutral is now drive. Drive is drive and shifting back into park makes her roll forward another 2 inches. Didn't have time to look for anything yet but hoping you guys can give me a heads up. I've googled it but not finding anything that relates to my problem. The only thing I've found is if reverse gos out the whole tranny is bad. I really hope not.

Thanks in advance.