Let’s Try Figuring Out Exactly Which Axle Nuts Are Causing Toyota To Recall 381,000 Tacomas

Whether you’re talking about commuter cars, SUVs, or pickups, Toyota has a near-unimpeachable reputation for quality (some of it earned, some maybe a bit exaggerated). The standard recommendation for any normie looking for a good car is to pickup a Toyota, or maybe a Honda. And yet, the Japanese automaker is not immune to making the occasional mistake. A great example is the latest recall for the Toyota Tacoma, affecting approximately 381,000 vehicles.

Toyota has stated that the recall concerns certain third-generation Tacoma trucks from the 2022 and 2023 model years. The new generation model is unaffected. The problem concerns welding debris which, in some cases, may have been left on the rear axle assembly. Here’s what Toyota says in its press release:

Welding debris left on the ends of the rear axle assembly during manufacturing could cause certain retaining nuts to loosen over time and eventually fall off, potentially causing a part to separate from the axle. If separation occurs, this can affect vehicle stability and brake performance, increasing the risk of a crash.

Toyota’s release on the matter does not state whether any accidents or injuries have occurred due to this issue. Nor has the Japanese manufacturer been specific as to precisely which fasteners could loosen due to the manufacturing flaw. Axle retaining nuts could refer to those holding the shackles, but more likely refers to the axle spindle nut. At this stage, NHTSA has not yet published details of the recall online, but that information should become available as part of standard reporting in due time.

[Editor’s Note: I’m thinking about what Toyota might be talking about, and I have a few theories. The first one is one I think is unlikely to be accurate, but I’m including it for thoroughness. The nuts that hold the rear axle to the leaf springs (and thus the rest of the vehicle) could theoretically come loose if the bottoms of the U-bolts were tightened against some kind of welding slag/asperity. Any shift of the U-bolt could move it off that slag/asperity, leading to a loss in tension, which could lead to handling challenges. 

But I doubt these are the nuts that are causing this new recall. I’m fairly sure it’s these:

Toyota says in the recall announcement that the nuts in question are “on the ends of the rear axle assembly,” which these are. These are extremely important and, if loosened, could lead to all sorts of chaos. Here’s what I mean:

The actual axle shaft (labeled “1” below) that provides thrust to the vehicle (it goes into the differential (labeled “5”) on one end and you bolt your wheel to on the other end) has what Toyota calls a “hub & bearing” pressed onto it. That hub and bearing sandwiches the brake drum backing plate against the flange at the end of the axle assembly. That’s this thing pointed out in red:

Here’s that flange on a Toyota 4Runner, which shares the basic rear axle shaft setup as the Taco:

As you can see in the screenshot above (full video below), if you remove those four nuts, the axle shaft and the drum brake backing plate can slide out, and theoretically this means your whole wheel could fall off. That would be bad.

These four nuts holding the hub & bearing onto the axle assembly flange make more sense in the context of Toyota’s quote in the recall notice: “…potentially causing a part to separate from the axle. If separation occurs, this can affect vehicle stability and brake performance, increasing the risk of a crash.” If Toyota were talking about the U-bolt nuts, the part that would be separating form the axle is the whole damn truck, which is a bit absurd. Then again, referring to the WHEEL as “a part” is a bit absurd, too. 

Still, I bet these are the four nuts that are causing this recall. -DT]

Owners of recalled trucks can expect to be notified by mail by late April. Recall notification timelines are typically tedious, so this isn’t unusual. Rectification of the matter will involve a no-cost inspection and repair, with dealer technicians retightening the retaining nuts where necessary [Ed Note: And perhaps adding a bit of threadlock. -DT]. In the event the loose nuts have caused other damage to rear axle components, this will be repaired at no cost to the owner.

Problems like these do occur from time to time, even with the rigorous standards of modern manufacturing. By and large, automakers try to eliminate these problems as much as possible, using advanced processes to catch problem fasteners before they leave the factory. Tools like smart wrenches log fastener torques, while automated inspection systems check parts for flaws prior to assembly.

But every so often, some edge-case fault manages to slip through. [Ed Note: This reminds me of the Jeep Wrangler track-bar bracket recall, which also involved welding issues. -DT]. The biggest issue is when it goes undetected for so long that thousands of vehicles get built with the flaw, requiring a massive recall effort. Perhaps the best example is the Takata airbag recall, which saw tens of millions of vehicles needing expensive replacement parts as quickly as possible.

If you’ve got a Toyota Tacoma of the affected model year, keep a close eye on your rear axle. If you’ve got any strange vibrations or noises happening back there, or a little oil leak, it would be a smart idea to park the truck until you can get it sorted. Stay safe out there!

Image credits: Toyota