It's just regular metal shavings. I got rear diff rebuilt a year ago and haven't checked the magnet since install (other than 500 mile drain and refill for both front and rear diffs). The trans plug I haven't pulled since install back in April. I was suppose to drain and refill at 2k miles after install, but it's been about 12k. It's just break in shavings, normal for new gears and such. Now if you start to see larger chunks (this stuff is like anti seize texture) then you should worry but as of right now it's fine
Sent while in 'Murica...