I don't think so. Try this: Remove shifter, put front side into neutral (you still have the cover off right?), then try to move the rear rail by itself (maybe gently pry with big screwdriver on sliding gear too) and see if you can get to rear-high. You should be able to do this without much effort. If it doesn't go then pull the detent ball and spring and try again. This will help to isolate the problem to either the shifter or t-case. If it works ok without the shifter then the shifter is your problem.