Brand new 3650 tranny with 5th gear noise?

Last week I got my brand new 3650 installed due to the dealer screwing up the TSB for the 3650. I was really happy with the Tranny til I got on the Freeway. 5th gear makes a noise which sounds like gear roll over... not to loud but loud enough to hear. My RPM's were about 2600.

So I guess my question is do new tranny's need to be broken in at all? I haven't really got on it, but was wondering if anyone else had this issue?

Thanks

Did you have a fairly small loud rattle in 5th gear going 2600 RPM or so?

Thanks,