Well, dirt creates friction, which makes noise. Its probably amplified by the ricochet down the axle and frame. This truck seems VERY sensitive to harmonics. I'm guessing the friction is momentary, like when the center of gravity of the truck shifts. This sounds like a "clunk", but its actually a very short "creak". I tried adding silicone lubricant (the aerosol kind) which is the only thing that has improved the noise it so far. I did it in stages to see what spot had the biggest impact. By far, the biggest improvement was when I sprayed the section where the axle seat sits on the axle under the u-bolt. I bolts seem tight, but I don't have any way of gauging the level of torque. Even if they were loose, they were just tightened 2 weeks ago. They shouldn't be loose already. I've not tried the rubber trick yet.
I tend to think it is quality control. GMs level of QC has taken a pretty big hit since around the time of the bailout. This is inevitably going to lead to more problems like this popping up, not just with one-off issues, but with the core design. Defects that everyone experiences. I remember reading companies like GM and Chrysler have a different engineering philosophy than most other car companies. Traditionally, when an engineer designs a vehicle, they submit a drawing to assembly, and that drawing is the final standard. If a parts manufacturer or assembly line does not conform with the drawing, then they are instructed to do-over, and match the drawing. Conversely, GM and Chrysler have a different philosophy; If a part manufacturer designs a part that isn't exactly to specification, GM and Chrysler won't necessarily send it back. If there are no immediately discernible problems with the non-spec part, they will amend the drawing to accommodate. This is just something I regurgitated from memory so take it with a grain of salt. I can't remember where I read it, but I've seen if a few times. If it was true, it sure would make a whole lot of sense, and explain why a lot of the issues we see with GM and Chrysler are shared by so many of their customers, and why the problems with other companies (Toyota's) seem to be mostly one-offs.
If they are off warranty, I would hope people are smart enough to not get it done at the dealer. Out-of-warranty work at dealers is usually drastically overpriced. Any mechanic worth his salt is not just going to replace a single bank if the lifters go. Get them all done. And when you get them all done, you might as well get the AFM deleted entirely. I've seen prices ranging from $2000 to $6000. I can't remember specifically where I saw it, but I seem to remember someone posting that they were recommended just to drop in a new engine It is not a small repair. I'm surprised there isn't a class action about this.
The oil didn't cause the issue, but it may have exacerbated it. The noise is caused by dirt between the leaf springs. Depending on what kind of oil was used, it can actually attract dirt, which will cause the noise. Only GM would design a leaf spring that you can't get dirty. Only GM would keep those leaf springs for over a decade before fixing it. The lubrication they use at the dealer is silicone based, and shouldn't attract dirt. The problem is that it washes away easy, so the noise comes back fairly quickly. I've heard that the issue is fixed in the 2019's. They moved the padding around or something. I don't know this for sure, but someone on one of the other threads has talked about it. I've also not heard of this happening on aftermarket leafs.
Yeah. I put this on a little over a month ago and it works like a charm 2017 Sierra 1500 5.3L V8 https://rangetechnology.com/afm-disabler/ Over 2000k later, and according to the economy computer, I've actually improved gas mileage. I do mostly city driving. Even if the lifters in this truck weren't garbage, I would recommend this device. It has drastically improved the way my truck operates, especially in low speed situations like parking lots and heavy traffic. The transmission seems to get confused less often and can actually decide what gear it wants to be in. I still get that clunk when downshifting between 3-2, but when my power-train warranty is up I'm going to do a full tune to hopefully fix that, disable AFM for good, and raise my idle over 550rpm to prevent the surging that is apparently common with the 5.3. If your lifters are already gone outside of warranty, then I would go as far as to do a full delete, which includes a new cam. If you take out of all that AFM garbage, the vortec/ecotec gasoline engines are actually second to none, and the engine will likely outlast the truck. If you are getting a range device, I would buy directly from range to ensure you get the latest firmware/model. I've heard stories about older stock being sold on Amazon which still have bugs that were resolved years ago.
Don't worry about it. The debate was stupid and pointless and derailed a legit thread. I think OP was the one who brought it back to life. Its still useful for other folks. The K2 trucks would have a pretty strong second-hand market by now, and this thread has some useful info.
You keep using that term "evidence". I don't think it means what you think it means. I think you are confusing "factual evidence" with "conjecture". Its an anonymous forum. Personal anecdotes from anonymous people are not "facts" and certainly don't qualify as evidence. I've never presented forum threads as evidence, or even pretended to. What i did say is that it was a "common concern". Right from my first post, that is all I have said this is. There are a number of threads of people being concerned about it. A quick search engine search will show that. You say I'm lying about these threads, but you've participated in many of them. Lots of people with differing opinions and results, but those threads do exist. Many of those people are saying they have positive results with cleaning (as I've linked). It doesn't make it evidence that a problem exists. Its just conjecture. But it is a concern that is stated commonly (hence: common concern). It could all be the same person with different accounts for all we know. I don't recall ever saying it was evidence. The only thing I would say would qualify as (weak) evidence that carbon is a problem is the fact that large manufacturers have spent not-insignificant amounts of money to fix this. We know this to be true because they have published it and its in the engine cut sheets. But that is an entirely different topic.
Just did a search. Very first post that came up. Just look at the topic. You may not believe the effects of carbon cleaning, but the guy who wrote this post clearly does. The second thread that came up, you actually posted in. " Yeah, its not "needed" I'll just be doing it for hp and fuel economy, probably worth about 10-15hp @ 70k" - truckguy82 " There's guys on audi forums that did before and after dyno's after like 70k miles, one guy with an rs6 made 100whp after cleaning lol" - truckguy82 You've clearly been following this issue for a while. I don't think you were lying when you said there were "zero reports" of actual issues, but I do think you were mistaken. The thread-count on this topic is definitely higher than "zero", and that's not including youtube or other forums. I'm not gonna spend the whole day sorting inventory on carbon post threads just cause someone called me a lair. Most people know how to use a search engine, so they can search it for themselves and see if I'm full of crap. I learned back in the 90's its a waste of time arguing with people on the internet. The original OP asked for long term perspective on the K2 series trucks. Whether you acknowledge it or not, these engines do build up carbon and there are strong indicators to suggest it impacts performance over the long term. The most damning evidence is that other manufacturers have devoted engineering time to fixing it. They wouldn't just do that on a whim. Those kinds of redesigns cost money.
I didn't call it a "big problem". I called it a "common concern". And it is. There are loads of threads about it. Just because most people won't notice the effects over a long period of time doesn't mean its not a design flaw worth mentioning. It is admittedly a long term concern. The number of people who have "issues" with this is significantly greater than zero. This forum is full of accounts of people who have had their 150k+ engines cleaned and noticed a significant performance increase afterwards. That increase is all of the performance they have lost over the life of the engine. It happens gradually, so most people aren't going to notice it until after they get it fixed. One of the reasons why truck manufacturers are able to get away with overlooking these things is because a huge part of the pickup truck market is made up of people who buy their trucks for show and will never actually use all the horsepower these engines are capable of. The suburban commuter who hauls his 21' Jayco to the campsite once or twice a year isn't going to notice his engine performance decline over a 5-10 year period. It doesn't mean its not an issue for people who want to buy a truck to "run it into the ground", or actually use the horsepower. The other major chunk of the market is fleet sales (businesses), which generally tend to turn over faster than individual owners, before carbon build up becomes an issue. I have a hard time believing that most vette or camaro owners will ever see a use for the full performance curve of their V8 after the first 10k when the novelty wears off. For the wealthy, those engines are purely for bragging rights, and will be traded up long before carbon deposits cause a noticeable loss in performance. And for nearly everyone else, they are mid-life crisis machines used to drive to work in morning traffic. Ultimately, I was responding to OP who was is the market for a K2 (2014-2018 range) truck. Its worth noting that Toyota saw this issue as worth fixing within that time-frame. Ford also implemented a fix for this during that time period. The K2 series GMs are behind the curve on this one and still haven't resolved it in their 2019s.
The rubber basically needs to cover anywhere there is tension between the leafs. This requires taking weight off them; so you will need a jack. You will need to gently pry them apart with something. Some have said they used a flat-head screwdriver wrapped in cloth. As for lube, be careful what you use. A lot of lubes will attract dirt. I think the recommended lube to use is a silicone based. You may want to power wash the leafs before you do this, just to get any existing lube residue, grime, or dirt off.
2017 1500 "Elevation Trim" 5.3L V8 21000km Purchased New Here is what I've learned (the hard way) are the common concerns with the K2 series. Lots of threads on each of these issues. Shake or shudder when driving between 70-120mph. This varies by person and seems to develop later in the trucks life. No one can say for certain what causes it, and everyone who has resolved it has done so differently. Mine started to shudder slightly around the 19000km mark. The common theory is that its a resonense issue. This means that nearly any source of vibration (tires out of alignment, bad driveshaft, etc) can cause the trucks frame to vibrate like a tuning fork. If this is true, then it basically means anything out of tune can cause it. The air conditioner condenser will fail. Its only a matter of when. There is a known defect in the upper drivers corner of the condenser. Fortunately, its an easy DIY replacement if you are inclined, and there are aftermarket options for when it does fail. Do not replace with OEM when this happens to you. The advanced fuel management system (cylinder deactivation, displacement on demand) will cause a lifter failure. The clock started ticking on this the moment the truck left the lot for the first time. GM claims they have fixed this issue, but there are so many people reporting this problem that GM claims seem dubious. Watch for lifter ticking noises. This is a very expensive problem (especially if your cam is damaged). If you buy a truck with warranty, get a AFM disabler ASAP. If you are off warranty, get it tuned out. It will save you thousands of dollars down the road. Leaf spring knocking. The leaf springs on this truck are garbage. They will cause noise the moment you introduce dirt. If you are a suburban warrior, then this won't be a problem, but if you use your truck to get dirty, expect your rear suspension to start making noise at some point. Valve carbon build up. This is a side effect of most direct injection engines. Other manufacturers are starting to solve this problem, but GM hasn't even budged on it. Over time, the performance of your engine will decline and may start to hesitate. This is like a frog in boiling water; you won't notice it happening. There are products you can spray into your air intake (seafoam, CRC, etc) that clean the valves, or you can prevent it with a catch can. If the truck has a lot of build up, there are places that blast the carbon deposits with walnut shells. Cleaning them yourself may damaged your catalytic converter, since all that carbon has to go somewhere. Vacuum pump break failure. This one is likely going to be another ignition-gate. People are going to die from this, but it seems that GM is going to roll the dice again and not issue a recall in the US. They were forced to in Canada. Transmission clunk on lower gears. Usually on downshift between 3-2. Still too early to say if this is going to cause transmission issues, but I've never had a transmission shift as poorly as this truck. There is some logic to owning an older truck where the most common issues are already known. That being said, if I had a time machine, I would go back and tell myself to not buy this truck. For the 2014-2018 range there are already proven to be better options.
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