Stat Monitor Repairman said:
This is the appeal of a Toyota / Lexus vehicle assembled and shipped from Japan.
Those Tundra engines manufactured in Huntsville, Alabama where Ray-Ray was hired during covid and skipped a critical step flushing out metal shavings from machining process.
The metal shavings or debris thing is certainly part of the problem, but it isn't the whole problem.
The issue is the front main bearing is failing, exclusively. The pictures of failed #1 mains look more like an overload or a clearance issue.
It is hard to imagine how manufacturing debris would plug off the oil feed to the #1 main every time, leaving all other mains and con rod bearings un touched. Not to mention there are some engines that have failed above 40k miles.
Toyota indicated they found the operation that was the source of debris and remedied this in 2023. However there are many engines failing that were produced after this date. Further the recall indicated hybrid engines weren't affected but there are several instances of hybrid models with failed #1 main.
The lexus version of this engine did not have this issue. Internet sleuthing by other forums has shown some credible pictures of a design change in the front main cap and its integration to the crankshaft support girdle (relative to the Lexus engine).
My personal take on this is the jaw fits for the main cap are having a tolerance stack issue between the block and the girdle. Combining this with a specific range of load and temp, the cap is 'walking' or 'shifting' to the point it is closing off clearance. With enough cycles, the bearing loses material and fails rapidly.
