Yeah I think you’re probably right. I just saw a lot of early 2007’s with diff issues here and there.
I think my problem was the Amsoil 75w-90 severe gear oil. My first several diff oil changes were with Valvoline 80-90 Dino. They always looked perfect like honey every time and at 112k, when I switched to Amsoil. Also never any metal in the oil. I’ve been doing a decent amount of towing since around 40k, mostly just for vacations. Nothing over the rated towing capacity of the Fj. Since switching to Amsoil, I made it 10k and everything went haywire. Now the oil is black, nasty had lots of metal in it and looked thin as water when it came out.
Anyways when I get my 3rd member back I’m absolutely going to be running Lucas 85w -140. All the gear shops I’ve talked to who build or rebuild differentials (including ECGS) all swear by it. I just don’t think Amsoil had the film strength to lubricant the bearings properly.
Final update, so got the diff back and everything is dead silent now. Every single bearing in the whole entire 3rd member was shot. So now I’m very suspect of the oil. Definitely running the Lucas 85-140 for sure and not risking the 75-90. The shop also thought is was lack of lubrication. Below are a some pics.