Trying to keep this as short/to the point as possible. I have a 91 Suburban with a Gen V 454 big block and a 4L80e. This is the drivetrain original to the truck, although it is possible the transmission is a rebuilt unit. It only has 73 thousand miles. After diagnosing low oil pressure, we found what we believe to be parts of a destroyed thrust bearing (see attached picture).

I have heard about the Turbo 400s and 4L80s producing too much line pressure, pushing the converter into the flexplate/crank causing thrust bearing failure. Now usually it seems like these are rebuilt units in race cars, but I have also seen the same thing happening with RVs and HD trucks pulling heavy loads.

My questions: What is the diagnostic procedure to test the line pressure without a scan tool? Does anyone have the chart with the correct line pressure ranges on it? Lastly, IF the pressure is too high, what do I need to do to fix it so it doesn't destroy my freshly built Big Block? Thanks in advance.

Non-magnetic shavings out of the engines oil pan, from (I think) the thrust bearing. The bottom ends of the rods looked beautiful. Open to suggestions on this, also.

 

Thanks. I hoping there isn't a problem internal to the transmission. I'll keep this thread updated with what I find.