Most people on the web say that it's the retaining clip in the axle, that goes into the diff and holds it in needs replacement. Or you can try to spread the clip out... So I tried that 4 times, while enlarging it by mm's at each attempt. Nada! Then, your suppose to replace your axle... Oh god, Cha Ching! My favorite was replacing the diff itself... Ooh, not inexpensive either, but closer to the truth.
After getting really frustrated and driving around with a floor jack and tools to fix this issue per each occurrence, I decided to drop the carrier this am, glad I did. Hope the pics are clear enough.
That spiral groove on the inside is what the c shaped retaining ring clings to. The grooves and the metal itself on this one are very worn, therefore the ring slips out upon a torque load and your on the side of the road wondering wtf. My car is lowered, so I couldn't see under it and had it towed home. I have roadside through USAA for a ridiculous amount of something around $10 per year, so I never chance anything... Tow it, flatbed...
I had another diff, so I didn't have to find another top to the diff. This was from the 4.11 gears I got from Aussieland out of that GTR. I didn't notice previous wear, why would I, but I'm sure my racing didn't help the situation. Anyway... Take the diff out and replace the top section, which contains the grooves. Put your new, btw, good luck finding one new, or used c-clip back in and your golden. No axle or complete diff replacement needed. FWIW
