Running rear tires with different tread depth on the bad for differential?
 

I recently hit a hunk of metal on the free way, which destroyed one of my partially worn Pilot Super Sports.

The tire shop replaced the tire and left it on the front.

The front tire's tread depth was 10/32" for the new one, 7/32" for the old one. And the rears were both 5/32". Hoping to achieve more even wear I rotated my tires, putting the 10 and 7 on the rears. I had actually asked the tire guy to to do this and he must have forgotten; he didn't balk at the idea though.

So then I read a post about replacing tires as a set on AWD cars because doing otherwise causes excessive wear on the differential and now I'm worried.

Will running tires with 3/32" difference in tread depth cause my differential to constantly run under normal driving conditions? Or is the different so small the differential doesn't "pick it up"?

Too minor a difference to matter, and we don't have a clutch type LSD either. In short, you'll be fine.

This. Subaru's AWD system is a finicky, whiny bitch when it comes to tires not being all the same tread. But a normal torsen LSD like ours doesn't care.