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This sure sounds like a collapsed Lifter and/or a wiped CAM. With the AFM, these engines (both the 6.2 and the 5.3) really like Full synthetic oil and regular oil changes. When it drops from 8 to 4 cyl mode, with old conventional dirty oil, it's my understanding that they are very susceptible to wiping camshafts. Many of the GM dealerships are using full synthetic only (no blends) and that's all I would ever use in our Yukons and Suburban.
Looks like the Steel got hot during the machining process. Perhaps their grinding machine ran out of cutting oil.
Had to replace me son's engine at 126K. Lifters failed and sounds like yours. Crankcase was full of metal. No hope of just replacing lifers.
That sounds like worse case lifter failure. This is why I recommend opening the motor and inspecting it before people go ordering parts before they find the extent of the damage
Sorry to hear about the personal setbacks. That sucks, man. But you have the right thought process. Yes, you can get by with just replacing the failed lifter(s), but I would do the whole bank of lifters on that side, along with new trays. But take care to do a good inspection of the cam for any damage through the lifter bores. Any damage or pitting at all, and that new lifter won't make 1000 miles, so the cam would need to come out. It would also be a good idea to replace the VLOM as they're often the source of AFM failures.
Thanks for the response. My failed lifter was on #4, are you saying replace the lifters on 2,4,6,8 or just 2 & 4 that share the same tray? Thanks for advising me on the VLOM as well. My heads are being machined as well so I can have that smooth mating surface. and valves lapped Any concerns with just using the same springs and pushrods(if they inspect okay) since I am sticking with the factory cam now, hopefully? I don't think there is any damage to the cam. As the truck was parked as soon as I first heard that tick, with only occasional running for a few minutes at a time for diagnosis. I will inspect it to ensure.
If you’re taking both heads off, then replace all lifters and trays, along with the VLOM. One root cause of lifter failure is worn engagement pins on the lifters themselves, and another is sluggish solenoids in the VLOM. It’s cheap insurance against future failure. And use OEM lifter trays only or you’ll be tearing it apart again in a few weeks. Ask me how I know ;-)
