Which build months are safe from lifter problems?

[wsteele]

When I had lifter failure at 12,995 miles, I had a very slight shudder in the engine when coming down from highway sustained speed. The vehicle almost felt like something spun around the driveshaft. It then operated normally for the next 15-20 min then all hell broke loose as I rolled in to town.

I’m convinced something’s wonky with my engine after the repair. Curious if the lifters are just beginning to fail or if it’s something else.

When these lifters fail, the internal mechanism that controls whether they can compress allowing the lower half to follow the cam profile, while the upper half compresses and doesn't exert upward pressure on the push rod, fails. It is a spring that breaks, so it really isn't something that starts slowly and then finally let's go, like say a bearing might. Kind of a binary event.

The failure on these lifters is caused by a broken pin lock spring inside the lifter. When that spring breaks, the lifter is unlocked "permanently" and thus the valve that lifter opens and closes is always closed thus unable to fire (hard miss). A hard miss will generate a check engine light (and usually a bunch of other notices that really have nothing to do with the actual miss). A miss definitely could feel like a shudder, depending on the mode you are in when it starts missing.

When you had your lifter failure, did they replace all 16 lifters, or just one bank (8 lifters)? Also, when you had your failure, did they replace any push rods and/or valve springs?

 

[TrueAt1stLight]

When these lifters fail, the internal mechanism that controls whether they can compress allowing the lower half to follow the cam profile, while the upper half compresses and doesn't exert upward pressure on the push rod, fails. It is a spring that breaks, so it really isn't something that starts slowly and then finally let's go, like say a bearing might. Kind of a binary event.

The failure on these lifters is caused by a broken pin lock spring inside the lifter. When that spring breaks, the lifter is unlocked "permanently" and thus the valve that lifter opens and closes is always closed thus unable to fire (hard miss). A hard miss will generate a check engine light (and usually a bunch of other notices that really have nothing to do with the actual miss). A miss definitely could feel like a shudder, depending on the mode you are in when it starts missing.

When you had your lifter failure, did they replace all 16 lifters, or just one bank (8 lifters)? Also, when you had your failure, did they replace any push rods and/or valve springs?

I’m hopeful that’s the case and I don’t get left stranded again. All I can compare to is the sensation I had when I first noticed an issue and that was a very similar shudder to what I’m experiencing now at idle. It’s really strange how my engine initially acted about 15 min before completely going to shit. I’ll keep everyone here posted as this may be a sign of bad things to come and a way to better predict a failure.

 

[R32driver]

I’ve got an interesting slight shudder developing at idle which I’m curious is the start of another litter issue. I’ll be taking it in on the 28th and reporting back here what they find.

It seems all gas chevys shudder at idle, that's one of their character traits. A quick google search finds lots of discussion out there covering many many years and models. We have 6 chevys running around the farm ranging from a '95 silverado up to our '21 yukon and they all do it

 

[brucesmays]

Mine was the #7 cylinder. Dealer said GM would only authorize the left bank of cylinder lifters to be replaced.

 

[Mikeamen1957]

GM issued a directive that guides actions under warranty by build date (truck build date). But that is just to give the dealer guidance on the required work if a failure occurs.

The actual cutoff date for bad lifters being installed in engines is March 5, 2021. Engines assembled before that date may have faulty lifters. The actual time delay between an engine being completed and the truck it is destined for being "completed" can be quite long (but I think normally is within a few weeks, hence the 3/31 cutoff in GM's warranty work directive).

You can see the actual engine build date by looking up under your truck at the back of the engine, on the drivers side. You will see a white sticker with a letter code (what plant it was assembled in), a 1 or 2 next (first or second shift), then a Julian date of the year and day it was assembled, the rest is the sequence code.

All of the above was posted on another forum by a guy who works at a GM engine assembly plant. He explained the faulty lifters suffer from the failure of an internal spring that locks the lifter so that cylinder is in fire mode. When the lifter pin lock spring breaks that lifter's valve will not open and you get a solid misfire in that cylinder.

He also explained that the suspect engines are also subject to faulty valve springs being installed (also due to improper heat treating), which explains the bent push rods on some engines (valve spring breaks, valve drops down into the cylinder where it it impacted by the piston and sent back up and eventually to a pushrod that is lifted by the cam and lifter in that cylinder on the opposite cycle stroke for that valve, bang, push rod does its job and bends minimizing other damage. Some speculate that this sequence of events can also cause a DFM lifter failure (due to the force of the push rod impact), I have no idea if that is correct or not, but it does sound plausible and would explain the "found: bent push rod and collapsed DFM lifter" report.

Can anyone tell me the manufacturer date on this one I’m looking to buy?

 

[Silverado4x4]

A= Mexico, 2203431= First number 2=2nd shift,20=2020, 343= DEC. 9th. So Engine was built on 2nd shift Dec.9th 2020 in Mexico

The questionable bad lifter dates were September 1st 2020 to March 4th 2021 so that motor was built during the questionable lifters from the manufacture of the lifters