Toyota Tundra Replacement Engine Teardown Finds Spun Main Bearing

A recently manufactured replacement engine from a 2022 Toyota Tundra suffered a spun No. 3 main bearing, an independent teardown found. The failure severely damaged the bearing and its crankshaft journal, raising an unresolved concern for owners who expected an updated engine to eliminate the earlier bearing-failure risk.

Date codes on multiple components indicated that the replacement V35A twin-turbo V6 was assembled around January 2026. The Tundra from which it was removed had approximately 64,000 miles, but the replacement engine’s own mileage was not established. Its internal condition suggested relatively limited use.

That distinction matters. A replacement engine installed in a higher-mileage truck does not necessarily share the truck’s accumulated mileage, service history or exposure. Without the engine’s installation date and operating hours, the teardown can establish the physical failure but not how quickly it developed.

Damage concentrated in the engine’s bottom end

Most of the disassembled engine looked comparatively clean. The oil pump, turbochargers, cylinder heads, pistons, cylinder walls, camshafts, timing components and gaskets showed little visible evidence of overheating, poor maintenance or obvious abuse. The upper engine’s lightly used appearance made the bottom-end damage particularly notable.

Metallic debris appeared in the lower oil pan. Further disassembly localized the major damage to the No. 3 main-bearing position, where the bearing had spun and badly marked the corresponding crankshaft journal.

Main bearings support the crankshaft as combustion and inertia loads pass through the engine block. A bearing that rotates out of its intended position can disrupt its oil supply and rapidly damage both the bearing shell and crankshaft surface. Once that process begins, continued metal-to-metal contact can generate substantial debris and circulate particles through the lubrication system.

That sequence is why debris in the pan does not, by itself, identify the initiating cause. Toyota has attributed earlier V35A failures to machining debris remaining inside engines after manufacturing. Pre-existing contamination could damage a bearing surface and initiate abnormal wear. Conversely, a bearing problem that began for another reason could produce much of the metallic material found afterward. This teardown did not determine which sequence occurred.

The damaged bearing differs from Toyota’s current inspection focus

Toyota has also introduced an improved front, or No. 1, main bearing intended to better resist certain remaining debris. For affected 2022-2024 Tundras, the company’s newer crank-bearing inspection uses a controlled impact, an accelerometer and software to assess the No. 1 bearing’s condition without first dismantling the engine.

The January 2026 replacement engine instead showed its severe damage at the No. 3 main bearing. That does not establish that the updated No. 1 bearing or Toyota’s inspection process failed. The inspection is designed around the resonant response associated with the front bearing, while this engine’s observed damage was in a different position. Whether the two issues share an initiating mechanism remains unknown.

The inspection procedure is more controlled than the informal “hammer test” description suggests. Technicians prepare the engine, attach an accelerometer to the crankshaft bolt and apply measured impacts to the pulley. Software evaluates the vibration response and available vehicle data before determining whether the engine can remain in service or requires replacement. It is a nondestructive screening method, not a substitute for a forensic teardown of an engine that has already failed.

Two engines warrant scrutiny, not a fleet-wide conclusion

A second reportedly failed replacement V35A has also surfaced. That engine carries a September 2025 manufacturing date and is reportedly locked, but it has not been disassembled in the available account. There is therefore no basis yet to say it suffered the same No. 3 bearing failure, involved machining debris or shares any other specific mechanism with the January 2026 unit.

Two reported replacement-engine failures cannot establish a defect rate, prove that every updated V35A is vulnerable or demonstrate that Toyota’s broader remedy is ineffective. A meaningful assessment would require the replacement engines’ mileage and installation records, production configuration, oil-analysis or debris findings, bearing specifications and failure data across a much larger population.

The first teardown nevertheless changes the question owners and engineers must ask. Replacement status and a recent manufacturing date are not, by themselves, proof that an individual engine cannot experience another main-bearing failure. The next useful evidence will come from disassembling the September 2025 engine and determining whether its locked crankshaft reflects the same bearing position and damage pattern—or an entirely separate problem.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.