Bought second hand, here is what I have done so far :
Tightened hanger and checked with PArk Tool Derailleur alignment, new gear cable,adjusted B screw. Running 34 teeth on back, XTR rear mech.
About to check wheel dishing/
Is it normal to have rear gears skip slightly on the full sus EPIC.
Any ideas greatly appreciated.
Check to make sure all of the shift housings are in good shape and are long enough. A section of housing that is too short or dirty/kinked can cause the bike to shift when the suspension cycles.
+2. If the problem persists, you might even try installing a little device called an Avid Rollamajig (I guess they're still available). It goes in the last loop of cable just before the rear derailleur, notorious for helping full suspension bikes with ghost shifting problems.
I don't know if you ever figured this out, but I was just searching for answers to the same issue. I recently built up an 05 Epic Comp frame from bottom-up. I love everything about the bike, but when the rear suspension is active, I'm getting ghost shifting- almost always it's trying to move the r/der up (easier gear), so it seams that it's pulling tension on the cable when the susp is active. I've tried a number of different things to get rid of it, but haven't found a solution yet and it's driving me crazy- mostly I feel it on fast bumpy sections, and on bumpy climbs (basically any time I'm pedaling through bumps). I know this has to be a resolveable problem, because I did a ton of research on this bike before I bought it and nobody even mentioned this issue, so it has to be with my build/ configuration. I'm running an XT rear der and xt shifters, nothing out of the ordinary. I'll try to re-route with longer housing both at the bottom bracket and at the rear der...