I had the axle TSB done. Does anyone know if they change your differential fluid when they do this TSB?

I'm curious because the Z's 15k maintenance program calls for differential fluid change at 15k.

Thanks

ps: the paperwork said "they replaced both rear axle joints for internal failure"

 

What year Z is this TSB for?

 

thanks guys. It's for an 03

By the way, I wasnt getting the typical axle sound everyone else was getting (during acceleratione tc)...

Mine was happening when I was creeping very slowly in a parking lot then applied the brakes. I would hear something that sounded like a twig snapping. I didnt really think it was the rear axle, but they did. I dont hear the noise as bad, but it is still there once in a blue moon. Should I have them re-do it?
thanks