JITIC

hey i just dropped a b16a1 into my 95 civic ex and i'm having problems with the right side halfshaft popping out. i've tried a 99 civic si axle which the spindle is smaller diameter. i've tried a 94 del sol si axle which fits but for some reason i've tried two of those and they've both popped out. i've also tried a 90 integra ls axle which is shorter than the del sol axle and it fits but will not stay in the transmission like it won't clip in. the code on my transmission says Y21. is it a problem with my tranny or am i not getting the right axles. i think i'm running out of options on the axles.