Ok I'm stumped. Rear end help please!

Ok so here's a new question. I set the pinion preload without the carrier installed to 28lb (I overshot a little but I figured it was ok). Then once I put the carrier in and snugged up the caps, now the preload is at 10lbs. What gives? I don't want to tighten it further unless I have to. I know the spec for new gears is 16-28 in-lbs, and used gears is 8-14in-lbs.

I do know the pinion was still cold from the freezer when I put it in, I suppose it's possible once it warmed up it lengthened a bit. Any other ideas?