Post by
amc49 »
https://forums.nicoclub.com/amc49-u275146.html
Fri Nov 24, 2017 7:30 am
It's a big belt sliding around between FOUR cones, two to a pair. As one pair opens up the other pair gets smaller in between. The 'V' space in between each two cones is the driver and gets bigger or smaller in opposition to what the other does. Making the belt settle down low in one pair and high in the other to change rollout distance and thus the effective gear ratio.
Normal ATX does have pretty much unpredictable fails too and one goes 200K while the one next to it on the assembly line only goes 100K. There is simply no way to tell as the differences can be so minor as to not be detectable on the assembly line. The transmissions are so easily affected by the way they are even put together it can lead to massive numbers of fails from 50 different reasons based on the trans design. The same with rebuilding them, one has to be super picky about attention to detail in every way, much more so than with engines if one wants a single unit to go the entire distance guaranteed. The more parts any mechanical thing has the more difficult it becomes to tell how long they will last.
Most people now follow the conventional wisdom that 'solenoids fix everything' and it seems nobody even thinks anymore that the parts can simply wear to have all the solenoids on earth fix nothing. I have fixed more than one trans with a simple say band adjustment (which have largely disappeared from transmissions) when the shops declared 'the trans needs to be rebuilt'. The shops don't like to do that any more as the results are too variable and they don't like having to mess with unhappy customers when the 'rig' didn't work. The rig of course CAN work for years if done correctly (I've gotten 20 more years out of a trans by using a 30 cent washer before!) but the skills to properly diagnose that are sadly lacking in today's shops. They do like the car dealerships do now, it's replace the entire trans everything all at once and then get the old ones rebuilt by a 3rd party that can be remotely blamed when things don't go right. That allows the spread of blame and also gets the shop the max cash it can get right off the bat. The way of the rest of the planet now, that allowing the hiring of much less skilled lower paid help as all they do is change trans all day long. CEO gets his bonus and everybody is happy except for the lower paid help and the way the planet works best. (sarcasm)
The CVT design is worth going out on a limb for Nissan over because they are (or have been) so much simpler than normal ATX, they can have more than 50% fewer parts (unless you count all the pieces it takes to simply build a chain) in them but the big issue is that chain to pulley friction thing which is 90% of the trans operation and the technology is still lacking to make the interface between those two parts as long lasting as they would like to see. Added to that is that when an older type non-CVT breaks in one gear then you often could limp the car home in another gear but with CVT that won't happen as the entire drive path still has to go through that CVT drive section. Meaning a much higher % of stranding out there and that makes nobody happy at all. Another CVT issue is the oil pumps, normal ATX does everything with up to 250 psi but CVT just to clamp the pulleys together tight enough to get a solid no-slip drive uses up around 800 psi and of course that leads to more reliability issues. And what leads indirectly to failures of the all important driving 'tooth bite' of the chain to the sprocket, once the tooth bite is gone from wear or insufficient oil pressure the trans slips and then any slip quickly removes the rest of the teeth gripping ability to bring the trans down fast.
I have no practical experience with CVT other than the drive type in industry (reinforced rubber belts on those instead of metal on cars, other than that the trans works the same) but I can tell what is what in trans blowups and I had zero experience in normal ATX either but every one I've ever built runs forever when I'm done with it. I have never paid for any car repair in my entire life and do all work including the most major type myself and for the last 40 years. Just call me super eccentric. Coming off Fords for forever, I'm tired of the way the company has gone so sh-tty with how they build the cars to intentionally break so they can sell you more parts. It seems they use the engineers more for that now than to make the cars last longer and it makes me want to throw up. Seriously, the Focus cars I have have failed so many parts and the replacement ones fail just as quick that I cannot even count them any more. Decided after a lot of years of Japanese motorcycle to try another line (Nissan) to see how bad the Japanese can screw things up, the domestic brands seem to have run that off a cliff. I personally don't like to pay too much for a car and paying too much and STILL having them break way too much stuff, well, that's simply unacceptable to me.