If this truck tows heavy then that will account for the Fe. All other metals are low, indicating this is generally normal lube performance.
What concerns me is the following statement:
Quote:
... and also basically towed straight off the dealer lot.
There is a general consensus among most folks in the diff industry that the VAST majority of wear occurs in the first 500 miles of diff gear life. Care should be taken during this time as the gears mesh and mate, establishing their wear pattern. If you towed heavily during this time period, you may have caused a bit of excess wear that is either still leaving some residual Fe in the unit, or even damaged the ring/pinion gears by forcing them into heavy service too soon. This may explain the high Fe count for such a short OCI.
Upon the next OCI, take the opportunity to remove the cover and look over the gears to make sure they have a good pattern and exhibit no signs of abnormal wear.