Rear differential noise on decel

[travish325]

Currently at 101k miles on my 2020 ST and have had this rear differential noise for a while, probably the last 25k miles at least. It was noticable but just sounded like some road noise before. I recently put on a AWR diff brace and now the noise is MUCH louder as I assume it's transferring the diff noise and vibration through the mount to the chassis.

The noise is only on deceleration off throttle/coasting, nothing while acceleration or under load. It's not a grinding or knocking noise, it just sounds like very excessive road noise like very worn tires (tires are new), no clunking or anything either. I am planning to change the diff fluid this week to see if that helps but I'm assuming it won't fix the issue.... any ideas?

 

[Cdubya]

I would think the diff fluid change would help immensely. Maybe it's old or the level is low.

 

[FORZDA3]

You’re describing classic worn differential gear noise, likely due to lack of fluid changes, or the original setup was off a bit.

 

[travish325]

Flushed and changed the diff fluid today and added some Barsleak Gear Repair. The noise on decel is still there, it is a tad less noticable but very obvious still. From reading it seems like it's a pinion bearing issue at this point... Anyone know how hard it is to replace that? I can't even find just the pinion bearing on a parts breakdown for the diff and I really don't want to replace the entire rear diff if not necessary