Wife's 2014 Yukon XL looks like it has a main seal leak. Started reading up on it and discovered a leaking valley seal or oil pressure switch can mimic a rear main. Hard to reach area. So I picked up an Amazon borescope, around $70. Works great!

BTW, dry as can be. Looks like I have a rear main in my near future.
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borescope.jpg (39.52 KB, 6 downloads)