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Comment by yareally | Hacker News Reader

Is this a genuine sentiment or just people upset that their favorite vehicle won't have a massive gas guzzling engine anymore? There are a number of people that also dislike trucks with aluminum bodies, despite that aluminum alloys can be strong (aircraft use them all the time) and it keeps your truck from turning into a rust bucket after 5 years of snowy winters. Car ownership is not always a rational thing and people will defend some strange platforms based only on emotion.

How are the CVTs in these trucks iffy compared to other CVTs? There's a number of reliable auto makers using CVTs for years, such as Subaru, Honda and even Toyota on their other vehicles. CVT transmissions have been in mass produced cars longer than most of us have been alive.

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CVTs (generally) rely on belts sliding on cones. With more weight, you need more torque, with more torque you get more wear on the internal components. This is a big reason why CVTs have historically targeted smaller cars instead of larger trucks.

When it comes to motor reliability, generally speaking a smaller engine with higher compression running closer to its peak output all the time will have more wear than a slightly larger engine that doesn't have to run at as high of pressures and load percentage. Lower RPMs needed for the same power output means less friction on all the components in the motor. There's a lot of variances in that so it is not exactly a given.

These kind of go away with more modern "eCVTs" which don't rely on belts and hybrid systems which can help even out that peak engine load challenge. But still, turbos will generally reduce your reliability. More moving parts, higher pressures, etc. The questions are, will the increased efficiency balance out the reduced reliability and will the motor reliability be the thing that does the car in at the end.

My understanding is that CVTs are more like a chain, i.e. a segmented metal belt.

It sure seems like they would be great for large trucks if they could be made beefy enough.

When people use the term "chain" in this context, they're usually thinking of it moving a sprocket with teeth that fit in between gaps on the chain. You're right that automotive CVTs are made with a lot of metal bits connected on a band for greater durability, but most would still just call it a belt as it relies on the friction between the edges of it and the cones to move the cones instead of pulling on teeth. Think the differences between a timing "belt" versus a timing "chain", but I do acknowledge a timing belt is usually non-metallic.

Sure, one could spend quite a bit of money making it even beefier with more and more exotic materials, but in the end its kind of hard to match the friction efficiency of well-fitting gears directly connecting the torque. You're pretty much guaranteed to encounter more friction on the belt sliding on the cones compared to well lubricated and properly made gears, and more friction means more wear which means shorter life.

But this is kind of the idea of eCVTs. Instead of belts sliding on cones (pulleys), they use motor/generators and novel gearset placements to change how the torque flows through the system. In this way friction is considerably reduced. There are no belts to stretch or wear out.

after hearing that the prius cvt didn't use a belt I had to watch a few youtube videos on planetary gearsets - mind bending stuff and dead simple to boot!

Both turbos and cvts are genuinely a reliability downgrade. It's because of fundamental and unavoidable reasons in each case. This applies to all vehicles, old or new, including ones they've already been used in for years like how turbo is a standard part of practically all large deisels.

"a number of reliable auto makers using CVTs for years" is an utterly valueless statement. It says, proves, disproves, or even merely indicates, nothing.

There are countless reasons for any company to do anything, including for a "reliable" automaker to use a less-reliable part or design.

Both turbos and cvts increase gas mileage. Simple as that. That one thing has become so important that it's now worth sacrificing other things to get it.

If you have a large engine and a small engine producing the same amount of power the large one will have a lot less load and so will last longer (assuming all else is equal - which is never the case). However it doesn't matter in practice as a modern car body and suspension system will wear out long before the engine in most cases.

The feel of a CVT in bigger vehicles is weird. Very difficult to get used to. Especially in ECO mode (Kia) which it defaults to.

>There's a number of reliable auto makers using CVTs for years, such as Subaru

Isn't the CVT going bad one of the main complaints people have with Subaru? Like at 100,000-150,000 miles. Other than the head gasket issue which was fixed a decade ago? Asking, since I'm in the market for a used vehicle, and the CVT reliability has me hesitant.

Subaru CVTs tend to burn up a solenoid in the valve body. They are available for $30-40 on eBay and take about 3 hours to do for the first time.

Dealers charge $3000 for the job. They install all new valve bodies for about $1200, and for some reason want 8 hours for the job.

I helped a friend do it after watching some YouTube videos, and we just swapped the one bad solenoid. 20k miles later, 120k total, everything is fine.

The problem isn't always the cars even. It's the entire repair model.

I just saw a video about a Nissan truck where you can't get transmission parts -- you can only buy entire transmissions. It's outrageous. Seal leaking? Time for a new transmission!

Yes that video from Dave's shop has been making the rounds. Its definitely a problem but honestly if the seal was removed and the exterior, interior, and depth were measured it can be purchased by spec instead of by a parts match for the exact transmission. That's like saying a furniture company won't sell me a screw that I lost, so the cabinet is worthless. I spec what kind of screw I need by taking a sample of another or measurements of another and go buy a generic screw.

CVTs are also much cheaper to manufacture than traditional transmissions.

That doesn't alone make them terrible though. CVTs have less complexity, so they will be cheaper. Dependable cars have CVTs for reasons other than cheapness.

For example, a dual clutch transmission is complex and expensive, but at the same time, I wouldn't call it better. There's tradeoffs in all types of transmissions. My car might have one, but if I were driving a truck, I don't think I would want a DSG.

Indeed, that was not a criticism.

Which also makes them cheaper to replace, which is good because you will likely need to replace it at least once in the lifetime of the car.

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