I can’t go any further on the combination of cap, ladder, bolts, crankshaft. To go further would require some major effort in actual testing and evaluation.
The wear pattern seen so far suggests the bearing is getting an uneven wear pattern. In these instances the bearing is still fairly smooth but has black marks that are from lube oil cooking. This is from heat build up in those areas. The black spots are on the edges and the corners of the bearing, both upper and bottom half. A video way up thread showed this somewhat clearly right at the end of the video with the failed bearing halves visible right next to each other.
Debris ( if caught early enough) will look like scratches and grooves . In the end phase of the bearing failure debris related failures have wear patterns that look like an overloaded bearing: the material is wiped around and chunks missing. At these heat levels the Babbitt gets amorphous and start to flow itself.
so the failures that have a strange wear pattern and are not destroyed seem to indicate 1) there are other failure modes at play 2) why some trucks are going 20,000 or more miles.
(debris related failures in journal bearings show up very very early in operation.)
To get a wear pattern like that the bearing is experiencing some form of misalignment.
The cap is being deflected one way or another ( “ cap walk” is a familiar thing with high horsepower engines).
The cause of this goes to how the cap is registering with the block ( jaw fit).
if this jaw fit is not rigid enough the cap can walk around causing the bearing to ride on the crank in a funny way leading to a wear pattern that looks like the crank has an out of shape journal.
because not every single engine is experiencing this, it looks like a statistically anomaly in manufacturing.
jaw fits slightly off, main cap bolts stretching slightly ( because a slight defect in manufacturing), or the ladder is having a strange interaction with the cast iron cap and also the engine block.
(I’ve seen this in large compressor crankshafts where the tie bolts weren’t tight, and when the main cap was not machined correctly, and when the main bore was not straight. In each instance a wear pattern was very clearly showing a misalignment. We could catch this issue before total bearing failure because the main bearings were instrumented with temperature sensors. )
The potential solutions would involve some revisions to these parts. It wouldn’t be a whole redesign. They’d also have to get to the #1 main to replace it.
they may even have an interim engine calibration that reduces load on the bearings as a stop gap.
the solution for the debris is just good old fashioned detective work with root cause analysis. Sample the debris for basic material characterization and trace it backwards in process from there.
( I saw an issue once where a rash of power steering pump failures was traced to an employee who was intentionally putting rubber bands in the pump…it all started with “ why is there a rubber material getting into these pumps?”)
( another anecdote: I helped lead a black belt project on a rash of thrust bearing failures that appeared out of nowhere. We twisted ourselves into bloody knots following standard procedures for this kind of situation. We beat up the manufacturing process every way we could. It turned out to be the outside vendor had changed materials and never told anyone.
one thing we found out during all this was the torque converter and pumps were putting 3x the axial force to the crankshaft as was specified in the design… so the bearings would have had a shorter life span regardless of the material defect)
