The concern with 4.10 gearing is that they can end up whining. Depending on which particular brand you get and how well it is installed. The quality of the shop you use really matters here. Before you select a shop to do this work, ask them about these issues. Ask them about previous 4.10 installations they have done. And ask them what they will do about it if it whines after they're done.
This last question is interesting because most of the shops you talk to may treat you like you're stupid for asking something like that. Of course they can't guarantee a 4.10 won't whine! Nobody would! The shops that have experience and know how to do it right will answer this question much better. This question, I think, is how you force a shop to admit whether they are experienced at setting up 4.10 properly. If they aren't successful enough at it to provide some form of guarantee on their work... well... consider what that means your chances are...
As for brand of gear... when you find a shop that actually knows how to do 4.10's, let them use whatever brand they've had success with. They know how to setup that particular brand to be quiet. If you have to tell them what brand to use, go to another shop.
And just a note... Richmond gears are generally regarded to be the strongest 4.10's out there. However, their straight cut design means that they _will_ whine. Period. I've never talked to a shop that believed they could make a 4.10 Richmond ring and pinion quiet.
Now, of course, if you don't care about such noises (if it's a race application, for instance), then none of this matters. Get the Richmond and have any decent shop install it.
As for cost... I think it was $1200 all told (labor, parts, everything) from a place that gave me a guarantee that it would not whine.
- Skant
