I currently have bravo 1 1.36 drives that I can not keep together. I would like to upgrade to an xr style drive. I've been looking around and there is a bunch of stuff out there used but I can't seem to find a pair of drives with the 1.35 ratio. I already own 3 sets of props and don't really want to start over. What I have found are a bunch of partials either uppers or lowers.
So my question is what determines gear ratio in xr drives? Is it a combination of the gears in the upper and lower or do they only make 1 gear ratio for the uppers and several different for the lowers. I'm just trying to wrap my head around what I need to be looking for, before I buy something that isn't going to work.

The drive ratio is determined by the combination of the upper and lower but all of the lowers are the same so to get from a 1.5 to a 1.35 you change the upper gear sets.

I suggest checking out Thebravoshop.net they have pats and schematics that you can look at and see the divfference. As I recall they even have pix of xr gears vs bravo 1 gears and you can see the difference there too.

http://thebravoshop.com/

32,
The older drives changed the upper gear sets to get the 1.36. When the XR came out Merc made different lower gears for the lower to make the 1.35, 1.5, 1.25 ratio. The upper 1.36 gear set has shorter teeth than the 1.5. When ever I put together a 1.36 drive, I use the 1.5 upper set and the 1.35 lower set, seems to be a stronger combination.
Hope that makes sense.
Dick

Thanks that was exactly what I was looking for. I ended up buying some xr's,