hmm well that is half good news then!
So it doesn't sound like straight cut gears(ie what reverse sounds like). Dude I don't know. What work did they do in the new tranny? just put new bearings in? did they have to replace any gears out? We've reached the end of what I know so, hopefully marlin will chime in.
Sorry I couldn't be of any more help
![Sad :(](https://board.marlincrawler.com/Smileys/marlin/sad.gif)