Can anyone tell me if Deore XT thumbshifters (we're talking old-school top mount, 7 speed thumbshifters) worked differently than Deore thumbshifters? I just got a pair of XTs on eBay and they seem busted. In friction mode, both the right and the left are basically spring loaded so that they are fully extended (lever away from you- bigger cog/chainwheel) at all times. There is no "friction" to speak of. You pull the lever toward you, and it just snaps back out.

My Deore 7 speed thumbshifters aren't like that and my first thought was they're busted. but then I wondered if the XTs used some sort of different logic, like they relied on the resistance from the derailleur to give them their "friction". That doesn't really make sense to me but they seem in good shape so I thought I'd check it out before I ask for a refund.

Can someone who's got XT thumbies tell me if these are indeed busted?