1992 Nissan 240/s15 differential swap

[Barnav1t]

I have a Nismo S15 Helical diff installed in my S13 diff housing with stock half-shafts. I have a "howl" that is occuring on deceleration. Almost positive it is not trans as it was just rebuilt. In fact, it was rebuilt because I thought it was the culprit.. There is a small amount of play where the half-shafts meet the diff. Do I need different shafts? And if so, what ones do I use? Any help would be great.