88 4x4 front diff trouble

[Dave884x4]

Ok, Transfer box works fine, front diff wont lock, took off the stupid diaphram, tried to engage it by hand and it would only move maybe an 1/8 of an inch, i dont think it is enough to engage it, seein git has to move the collar over the splines. what would be my first action here, do i need to pull the diff, or what, any and all opinions would help, dont want to do double work for no good reason, thanks.