I know this is an older model LX SL-M580, the first I am aware of with dual-release. I found and odd behavior and wondered if anyone knew why Shimano would set up this shifter in this way. So here goes... When in gear 9 I can downshift (smaller to big ring) 4 gears, at about gear 6, I can only get 3 gears, at gear 4, I can only get 2 gears and I need an extra push to get to the granny. I saw another thread about compatibility (below) and the OP posted the same information in a different manner but it was never truly answered. A couple of things: This happens with the shifter off the bike as well as installed, so it is not a cable or derailleur issue. I have 5 of these sets, all 5 are exactly the same model and exhibit the same behavior, 4 of them brand new. 3 bought of them are bought a year later from a different vendor so they are definitely a different lot. I think the behavior is as designed, but why when standard Deore grabs 3 gears all the time? Just curious... Here is the other thread:Shifter - Rear Derailleur Compatibility / LX SL-M580 9spd Shifter with XT M761-SGS