You say it won't shift. Does that mean it won't go out of 1st? Have you pushed the engine to the end of the RPM band to see if it eventually changes? If it does'nt, then it's in the valve body. Remove and dismantle it whilst ensuring that all the valves and springs are stored in correct relationship - u can use a piece of corragated iron roof sheeting to rest them in perfect positioning. Or get a piece of cardboard, place a ruler against its end and bend the cardboard to make triangular corrugations. Works well. You don't have anything to loose. That's what i'd be doing as I found several stuck valves in my time that caused havoc. Sounds like a stuck one - two shift valve mate! No rocket science here. Most probably it's been caused be the entry of some foreign matter in the vavle body. I'd say it's entered the hydraulic system during replacement of the pump seal as that is an area where clean filtered fluid enters. From there on the dirt would go straight to the valve body. Just before I go, did you ensure that the throttle pressure cable has spring tension on it? It may be not returning. It needs to pull out and retract without any binding at all.... Good luck. Rob