In other words, leave it and let them "grind it out" until they mesh??
Rick, I got you message, but I'm not sure my replies are going through, probably doing something wrong. Let me know if you got my message.
There may not be anything "wrong" with the gear in the first place. Maybe the gears are made with a tooth pitch that might be stronger and just have a natural whine to them. I know the gears I had made by Albins for my 930 were still helical and not straight cut, but still had some whine to them.
Fifth is the two gears nearest to the R&P.
Question would be has the noise been since new or developed in recent times.
ZFQ did have some early problems with the nut at rear failing under heavy load which allowed shaft end play & bearing preload to relax. I believe there was a change made to help fix this. Attached pics of lower shaft breakage, this trans may have been subjected to some large forces imposed by the nut behind steering wheel and should not necessarily be seen as a ZFQ fault, however IIRC there has been more than one instance of this type of failure, not necessarily to the same amount of distruction.