Did an oil change yesterday at about 5k since the last one. A bit longer than I normally let it go, but I didn’t have time before driving the X to Kansas recently. I’m sending a sample from every other change to Blackstone for an analysis. The motor seems to be aging well (about 25k on it now) so it’s mostly just curiosity. 8+ quarts of 5w 30 full synthetic. I also changed the rear diff oil and put a new gas cap on the car. The tether on the old one snapped and I was going to live with it, until I dropped the cap a few too many times when fueling in a hurry.

The Quaife has been in for roughly 15k, and this is its first oil change after I did a break in service at around 1k on it. Definitely some metal mud on the magnetic plug I use in the diff. All diffs make some metal, but I’m starting to suspect that I either screwed up the output bearing pre-load, or the pin/ring gear adjustment, or the pinion bearing is slowly going bad. That is the only one I didn’t change when I built the eBay diff because I didn’t have the right tools to do a good job, and the pre-load was spot on when I tested it.

Of course it could be the Quaife too, which is essentially a very dense collection of gears. But I suspect my handiwork long before I’d suspect the quaif. Regardless, I only get a very, very slight hum in cold weather, at low speed. Which could be any number of things I guess. Definitely coming from the back of the car tho and only from a dead stop to maybe 25 mph, in cold wx when the car is cold.

A “keep an eye on it” issue.

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee