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Discussion Starter · #1 ·
My brand new, 2021 GMC AT4 was diagnosed with a "bent" lifter.

The other day, I was rolling down the highway at about 50-60mph when I started hearing a clanking/knocking noise followed by some vibration. I took it easy getting it home as I had no idea what was causing it. I didn't drive it again until I took it in to the dealer. When I started it up, it began making the noise and vibrating again, even while idle in park.

They told my it was a "bent" lifter. Only have 9.5k miles on my truck. They are ordering me new parts, but I'm worried they're just gonna throw the same new factory lifters on there and I'll run into this same issue again.

Has anyone else had this issue? More importantly, has it led to any other components in the engine and/or transmission to fail?

Thanks.
 

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And yes...the dealer is going to put the same crap back in the motor. That's all they're authorized to do.
 

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You can thank the EPA and Congress for forcing them to try to get the very last .01 mpg out of these motors. It's a flawed design from the get-go but it's what GM came up with to try to meet the CAFE standards. They cannot put alternate parts in the motor under warranty. GM and the government would never allow it.
You can put in aftermarket, non-AFM parts but that would void your GM warranty, even though it would become more reliable. Catch-22.
Let the dealer fix it. It might not ever happen again. If it does, you might get a brand new motor out of it.
 

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Discussion Starter · #10 ·
Okay thanks for the advice GBSierra. I would imagine it would do the exact same thing if they are gonna throw on the exact same parts. But I'll cross my fingers and hope for the best before throwing on the AFM delete and losing my warranty.
 

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Not all AFM motors fail, some fail early (<50K), some fail very late (200K+). Hit-and-miss, that's what it is. Like Gary said, let the dealer fix it and use your warranty accordingly. If it fails again, you might be in for another motor.

No, these things shouldn't happen, but unfortunately the regulations have put us where we are at and we just have to live with it. Grass is not necessarily much greener on the other side, either.

Hope you get it all taken care of.
 

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There is a known issue with the 2021 5.3 and 6.2 motors for bending lifters before 10k and there is not currently a fix for it other than replacing them with the same ones. Seems to be happening more with the 6.2 than the 5.3.
 

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On my '14 6.2 It dropped a valve and they replaced the heads. So I would assume instead of replacing a lifter and rebuilding the heads they would just replace them.
 
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