So my Tahoe had been having troubles for a while, where the front diff would make a repeating noise when it was set in “Auto” AWD. Full 4WD and 2WD were fine. Differentials were way past my comfort zone (I was guessing it was a CV joint in the front) so I had a shop diagnose it.

They found the rear, driver-side axle shaft to be bent* just enough that it was causing the system to think the rear was slipping and engage/disengage the front wheels, but not enough for me to notice while driving. They quoted $1200 to fix it.

“Axles shaft replacement? I can do that! Easy.” Just pull the diff cover, undo a retaining bolt, pull the C-clip off the axle, slide the axle out, replace the bearing and seal, and put the new shaft back in. No problem!

Took me most of a day (needed to borrow a slide hammer for the bearing and the C-clip did not want to cooperate), but I did all that, put the wheel back on and took it around the block for a test drive. Before I made it past my yard the dash lights up: ABS light, Traction Control light, and “SERVICE STABILITRAK” on the info display. Awesome. What did I do wrong?

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For starters, I broke this piece with the slide hammer and forgot to replace it. After searching all over and pouring through many service diagrams, turns out it’s just a piece of plastic used to help guide the axle in. Not necessary to replace. Okay... moving on...

That was Saturday. Since then (Thursday) I’ve been trying to diagnose what I did wrong before I pull the axle back out. My dad is active on the repair forum Batauto.com and suggested I talk to the folks there. After some troubleshooting with the laptop and pulling the speed sensor it looks like the reluctor wheel (toothed piece that spins with the shaft and is read by the speed sensor) got tweaked at some point and isn’t lining up right. So now I get to spend another full day redoing the whole thing and replacing the seal again (and possibly the reluctor assembly).

For what I spent on parts so far, I really only saved about $800. That’s still a decent amount (I can now “justify” buying this fancy shifter for my M3), but on the edge of being worth it for two weekend days being chewed up and a lot of aggravation.

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Next time I might just pay a professional and spend my time on the “fun” stuff (race car build).

* This is a vehicle I bought from one of those non-dealership used-car lots. I’ll never do that again because I later realized this was a vehicle, like all of their vehicles, that was purchased from auction and repaired by them for as little as possible. It looked nice from the inside and outside, but once you started looking more closely you found a bunch of bad wiring, missing pieces, and junkyard parts. Little things, like the cruise control, never worked, and I’ve found problem after problem due to somebody’s shoddy repair work. I want to crush this truck, put it in a sack, hurl the sack into a river, and hurl the river into space. Of course, I could have had the same issue buying it on CL, but the odds are lower there (not by much).