AWD not catching sometimes. Is this normal?

[pinoyboy]

So I installed the awd on my Evo G35. I used the longest driveashaft and made sure that all the gears were seated correctly. However, sometimes when under load, especially in reverse, the gears don't catch. If I give it a little push however, it will catch.

Is this normal? I put gear lube on the joints, was that a bad idea? thanks in advance