Posted by Jason Locke on 6/3/2022 to
Postmortem
We here at Stage 3 are pretty hard on our trucks, but despite the amount of wheeling we do, we've only had a few issues on company time (though a few more in our own personal time). However, on our 2021 Sasquatch Bronco Build's first real outing into the dirt, we managed to break something that caused all sorts of havoc with our Bronco's ABS, traction control, drive modes, AdvanceTrac, and cruise control. What the hell happened to cause issues across all these different systems? Well, welcome to the world of integrated systems that are all tied into a single sensor and how the failure of a single bearing can cause so many systemic problems. The root cause of all of our issues was a failed rear axle bearing, but that failure which usually wouldn't be all that annoying caused a lot of problems for our Bronco, and the reason why is fascinating and shows the pitfalls of adding technological systems to trucks all tied into a single point of failure.
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What actually failed on our 2021 Bronco?
The part that actually broke on our Bronco was our rear passenger's side axle bearing. Now, it's not super-uncommon for axle bearings to go bad, especially when a truck gets beat off-road. However, with as few miles we have on our 2021 Bronco Badlands Build, it's definitely not a great look. Unfortunately, we didn't get a real detailed analysis from the Ford dealership other than that the bearing race "had came apart [sic]", though we're not certain if the bearing "came apart" when they removed the shaft or if the bearing was already chunky before that point, but in any case, this was only the beginning of our problems. One the bearing had failed, it caused at least some damage to the ABS tone ring on that side of the truck, which then caused wonky readings from the ABS sensor, which lead to the various issues with electronics we were seeing. The ABS system serves as the base information gathering tool for essentially the rest of the Bronco's traction control-related systems, so bad information from the speed sensor means that all these various modes and system could no longer operate effectively.How did our 2021 Bronco's Axle Bearing Fail?
How our particular failure occurred is not exactly known. Considering this only happened to one side of the truck, we haven't been able to find other folks with a similar issue (at least not on the rear), and that the rear axle as a whole is very similar to a lot of the other Dana M220-equipped trucks out on the market, we're willing to chalk this up to a freak, one-time event. With Ford getting their bearing supply from companies like SKF, Timken, and whomever else, a bad axle bearing or two is bound to end up in the world somewhere, and we're just born lucky. The bearing itself could've had a component not quite machined to spec, had a lubrication issue, or wasn't adequately hardened before being shipped out. However, it's also possible that there was an issue with final assembly on Ford's line, but I have a feeling that if that were the case, we would've run into a issue before going off-road. If I were to put money on it, I would guess that we most likely ended up with a 1 out of a hundred thousand bad bearings, but it is hard to say without having the failed component.What was Fixed on our 2021 Bronco and How Much Did we Pay?
The bad news about our Bronco's axle bearing failure is that a lot of stuff on the passenger's side rear axle had to be changed out. Our good friends over at Surprise Ford ended up replacing the entire right rear axle assembly with a new bearing, tone ring, and ABS sensor. After we got the truck back, all the errors were cleared up and the Bronco drove just fine. As for what we paid, the sum total of parts and labor was ZERO. The entire cost of the fix was covered under our Bronco's bumper-to-bumper warranty, which is extremely awesome, considering we broke the thing off-road and have video evidence to prove that we didn't just drive this thing like grandma and we SWEAR we never took it into the dirt, Mr. Service Advisor, sir. While the repair work was free, we did lose the truck for a full week, which doesn't affect us too much, but would definitely be a huge hassle for your average Bronco owner.