Ghost Shifting Uphill
 

I just bought a 2010 Trek Fuel. Replaced tires and chain. Works pretty good except its ghost shifting up hill. It was doing this with the old chain as well but think its worse now. I also adjusted the rear derailleur alignment since putting on the new chain but it looks pretty straight. Any thoughts on probable cause, cassette, cable?

Ghost shifting is usually caused by frame flexing under load or by poor derailleur alignment under the cog you want it to stay in. Since this is a full suspension bike, it's possible one or more of the pivot points are worn and letting the rear triangle flex under chain tension..

I've had worn-out cassettes do that. Smallest / most used cogs will wear out first, so if it only jumps in certain gears, that's likely your problem.

Ugh, really hope I don't have to re-bush the pivot points. Thinking I will try a cassette first. Thanks for you're input.