Ford Bronco Owners Say Trail Turn Assist Is Breaking Diffs

Owners have reported trouble getting warranty repairs when they discovered damage to their differentials, but aftermarket modifications may play a role.

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The Ford Bronco has been lauded for its off-road credentials since launch. It achieves its prowess through a combination of mechanical fundamentals and technology. Now, though, some owners are drawing issue with the Trail Turn Assist feature, accusing it of breaking their modified trucks.

As reported by CarScoops, the problem concerns the rear axle assembly. Two owners have reported plug welds on the axle tubes failing on the Bronco6G forums, with the tubes having shifted relative to the differential assembly. In one post, the owner says that Ford reportedly denied warranty coverage for the problem as he had driven the vehicle off-road. Another poster alleges that they couldn't get a repair under warranty due to aftermarket suspension mods. So far, it seems to only be affecting rigs that are heavily upgraded with larger tires to boot.

The Bronco features Ford's Trail Turn Assist system, which locks the brake on one rear wheel to reduce the vehicle's turning circle. Trail Turn Assist is intended for use off-road on soft surfaces to enable the driver to execute tighter turns in difficult situations. Owners have been placing the blame for the problem on this new feature, with one stating "The forces from one brake being locked up, and the other side unlocked, combine with the forces that want to cause axle wrap or pinion lift (twist) are too much for Dana spicers [differential] housing."

It's plausible that Trail Turn Assist could play a role in this issue, particularly given the Bronco's rear brakes are attached to the axle tube. Plug welds on the assembly could fail when the feature is used on modified vehicles, particularly on sealed surfaces where it was never intended to operate.

When reached for comment by The Drive, a Ford spokesperson responded, "Ford is not aware of any claims with Trail Turn Assist when the feature is used as intended on loose surfaces while off-road, as instructed in the Bronco's owner manual. If an aftermarket product causes a Ford part to fail, the cost of repairs and any related damages are not covered by Ford."

While some have accused the Dana differential of not being up to scratch, that would suggest a major oversight by Ford. Typically, OEM vehicle testing is hardcore and exhaustive, and the Bronco's development was no exception to that rule. It seems unlikely the stock differential wouldn't be designed to handle the loads from the Trail Turn Assist feature, but when drivers begin to add aftermarket components, extra stress to the vehicle has to be factored in.

It's worth noting that these aren't just trucks with lift kits, either. Several have completely redesigned suspension systems for high-speed desert use. While Ford builds Broncos knowing that owners might tweak them, the automaker doesn't claim to cover fixes when they're tied to extensive alterations.

Ford explicitly states it will warranty the Bronco for off-road use, given the vehicle's clear design intent. Whether that extends to vehicles with aftermarket lift kits and significantly larger wheels is another thing entirely. The company has always noted that failures caused by mods aren't covered under warranty, so the root cause of the issue will clearly play a role in any and all cases going forward.

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Updated at 12:10 p.m. ET on 05/16/2023: Details were added to this article to more accurately reflect the modifications made to affected Broncos.

Updated at 1:40 p.m. ET on 5/16/2023: This article now includes a comment from Ford on the situation.