the very first thing you want to do is make sure the tranny has the proper amount and type of lubricant in it. These can get a couple of different types of fluid , and the only way I know of for sure is to look on the tranny for a yellow label. it should state what type. If no label, maybe your original owners manual would have it. The correct fluid and level is important, especially as it gets colder. The reason I suspect fluid level is because you have noise in more than 1 gear.
Geoff