Likely a dumb question, but here it goes. I'm fairly new to Chevrolet, 61 and just bought my first 4 for work and

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tgwhit12

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pleasure about 3-4 years ago. My first was two used 2500 vans. The 4.8 was ticking when I bought it at 85,000 miles and it is still chugging right along 25,000 miles later. One of the Tahoes, former cop car I bought started ticking and I drove it 2,000 miles home from northern NY to Memphis. it bashed up the camshaft pretty badly. I did the LS2 lifters in it, camshaft and new o ring oil pump etc. It runs great now. I guess what I'm puzzled by is that I thought I understood these v-8s to bullet proof except for the AFM / DOD lifters. But, the Tahoes (both former cop cars) never had the AFM / DOD turned on. They came with those features programmed out. The vans, I thought, never had those features turned on either. Neither of them even have the sticker on the brake reservoir. So why are these top ends having trouble, if it never had DOD type lifters?
 

B-train

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Poor engine oil change schedules is the most likely cause. Vans were probably contactor or delivery under lease = change at oil life indicator (approx 7500 miles). Police cars may have been the same. If they did less than oil life monitor miles, they have TONS of idle time followed by hard running.

Stick to 5k max on oil change intervals and you should be fine. You could also try the Marvel mystery oil, sea foam, or ATF as an additive on a couple oil changes to clean out carbon and varnish buildup that leads to noisy lifters.
 

Marky Dissod

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The Oil Life Monitor is a great idea ... in principle. In practice, feel free to apply a correction factor.
NYC cabdrivers who change oil & filter when the OLM hits 50% obviously want to keep that car forever.
Some people won't change oil & filter before the OLM get under 15%.
Some never let it get under 25%.
Pick your poison.
But, the Tahoes (both former cop cars) never had the Engine Half@$$ turned on.
Every PPV & SSV I've ever 'met', if that year had Engine Half@$$ available, had Engine Half@$$ on that PPV SSV until the 2nd owner disabled or deleted it.
Are you SURE the Engine Half@$$ bug-feature was disabled by the original gov't owner?
...
Even if Engine Half@$$ is disabled, not changing the oil often enough ages the two-mode lifters more quickly.
High RpMs age two-mode lifters even more quickly.
Best to replace two-mode lifters with real lifters.
 
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tgwhit12

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So, am I hearing that the 11 and 13 Tahoes, plus the 07 van came with dual type collapsible lifters even if the DOD came programmed out at the time of purchase. I have two of the cop Tahoes and I feel pretty sure that neither have ever entered AFM and I thought I read on here that the programming for PPVs had the AFM deleted. I definitely did not do anything to program the 11. I just started driving it and it has never cut to 4 cylinders. The 11 is the one that had lifter failure coming home from NY.
Does my 07 van then, have DOD style lifters in the 4.8 even though it has no AFM tags?
 

petethepug

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Look on the glovebox door for the engine code and / or simply google if the vans that year even offered AFM.

For the full size SUV only the very, very early 07 got AFM hardware that was dormant. Of those very few there are only a handful still known and around.
 

RET423

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The AFM system lasts longer if it is programed to never actuate but the lifters are still a point of failure, a proper delete of all the hard parts is the only way to insure you get the long reliability these engines are known for
 

Marty_S

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pleasure about 3-4 years ago. My first was two used 2500 vans. The 4.8 was ticking when I bought it at 85,000 miles and it is still chugging right along 25,000 miles later. One of the Tahoes, former cop car I bought started ticking and I drove it 2,000 miles home from northern NY to Memphis. it bashed up the camshaft pretty badly. I did the LS2 lifters in it, camshaft and new o ring oil pump etc. It runs great now. I guess what I'm puzzled by is that I thought I understood these v-8s to bullet proof except for the AFM / DOD lifters. But, the Tahoes (both former cop cars) never had the AFM / DOD turned on. They came with those features programmed out. The vans, I thought, never had those features turned on either. Neither of them even have the sticker on the brake reservoir. So why are these top ends having trouble, if it never had DOD type lifters?
175K on 03 yukon bought last August and valve clack it very noticeable. did you try the additive idea? did it quiet things? on flip side should I expect to do some engine internals that scare the hell outta me? thx for any/all knowledge you have on this. somewhat joking here, "didn't know Dept of Defense made lifter rods." so far been making sure to idle after start long enough for the noise to quiet down and it does after a minute or 2.
 
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tgwhit12

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The AFM system lasts longer if it is programed to never actuate but the lifters are still a point of failure, a proper delete of all the hard parts is the only way to insure you get the long reliability these engines are known for
That is what I needed to hear. Thanks RET423, that makes sense.
 

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