Bicycle Mechanics - Here's an odd problem with a rear deraillieur.

Discovered this on my afternoon ride. I have a 9 speed Shimano XT rear deraillieur with a Triple on front having the 27 speeds. Here's the problem I only have 4 gears that will work on the rear the 9th, 3rd, 2nd, and 1st. So instead of having 27 speeds, I only have 12. What is up with that? The cage is not broken and I can not find any bends.

Is it only happening on one front ring?

On every single front ring.

What happens when you attempt to ride in one of the remaining cogs? Are you unable to shift into one (misadjusted cable length/tension, perhaps), or does it skip under pressure (worn cogs)? Make sure your rear derailleur cage can move through its full range (probable, since you say you can get both 1st and 9th gear), that the cage is straight and properly aligned with the frame, and that the cable is not slack in high gear.

The problem is most likely in your shifter UNLESS....

Did you happen to replace the chain with a chain that is too wide for a nine sprocket freewheel?

Assuming the chain is OK, my guess is the problem is in the shifter.

Maybe you have GripShift, specifically the ESP models? They are designed for ESP derailleurs, which require twice the cable travel of a Shimano derailleur. Just a guess. Other possiblilties that come to mind: you have the cable anchored incorrectly at the derailleur, or your shifter is faulty.

You know, derailures are really pretty reliable. With the exception of the hanger getting bent or the derailure getting dirty or the derailure spring wearing out (rare), they usually don't cause much problem. The problems with shifting is usually somewhere other than the derailure.

I have XT shifter pods, and it's a 9 speed chain.