Nissan Maxima CVT nightmare /Fixed it so far

[vacerator]

Lifetime means

for the lifespan of the component (trans.) in this case. Asin fwd automatics are/were know to develop shiftin problems or worse by 80,000 miles. VW used them in the 90's.

 

[suburbanmd]

Toyota hybrid CVT

This interactive animation of the Toyota hybrid system

 

Toyota Prius - Power Split Device (eahart.com)

 

works with the Flash Player 2022 extension on Microsoft Edge browser.

 

The hybrid system also serves as the transmission, with permanently engaged gears and no bands and clutches. Clever and very reliable.

 

[statomatic]

Millenial anti-theft device

Never wanted an automatic transmission, mostly because most of the French mechanics don't know how to maintain them.

My good old 87' Peugeot 309 has a five gear manual transmission, I drove something like 30km and found out the 3rd gear sounded funny, checked the oil level (lifetime lubricated), there were no oil !
Added some oil, still runs, try this on an automatic transmission !

 

[askolover]

I may put that same sticker on my 5sp VW!

 

[henene4]

Had a 5 speed Golf as my first car - hated it.
Mostly because of the clutch.

Now have a VW Polo 6R with a 7 speed DSG.
Bought it used with 42k km on it and getting close to 100k now in my 4th year having it.
Did not have any transmission issues per se yet.

It does have 2 "quirks".

First, since it uses a clutch, off the line, it can be jerky if you step onto the gas like you could on a torque converter.
If you lift your foot off the break, there is a split second before it starts engaging the clutch for first gear.
So if you directly step onto the gas hard, the system snaps the clutch closed for first gear. No inherent smoothing from the TC there.
So you gotta lift your foot of the break early and not hurry to get onto the gas. Once it engaged the first gear you can immediately give as much gas you want and not get that jolt.
Same goes for a kick down - it skips gears there and might engage the clutch quite quickly as a result.

Second is after extreme temperature changes the clutch slip points aren't exactly where they need to be anymore.
The electronics learn that automatically, but it might take a drive or so until it does.
You feel it struggling which gear to choose and engaging gears either very sluggishly or way to aggressively.

I do think that since I have a very light car and never had an automatic before, I am lucky and the clutches can handle the load.

On people driving bigger cars and driving it like a torque converter they can quickly wear the clutches out.
Another issue is standing very lightly on the break while rolling towards a stop light or so - there is a certain area of break pedal before the clutches disengage and if you let that sit to long that wears them out easy.

CVTs were ment to be super efficient since you'd always have the right RPM.
But people didn't like that exact thing, so they programmed CVTs to act more like normal transmissions.
And they have technically parts susceptible to wear under usage.

Torque converters are big, heavy, parts intensive.
They either loose some efficiency due to slip or loose some reliability due the the TC lock up system.

DSGs have continuous torque and incredibly short shift times.
But they have wearing parts and fully emulating the comfort of another car makes that worse.

 

[foraloysius]

DSG

I guess that's a typical DSG problem. It can only shift one gear up or down at the same time, in contrary to most other automatic transmissions. In some situations this leads to hick ups. The DSG was the answer to the problems of the automated manual transmissions like my Smart has. The DSG took away the pauses during shifting, but the downside is that it can shift only one gear at the time. Both systems need a little patience to use, but the DSG less so than the original automated manual ones.

 

[henene4]

Automated manuals

Automated manuals were always kind of meh.
The mother of a friend had a Smart as a loner and she described it as if you were driving, but someone else was doing the shifting - but that person wasn't very good at it.

The DSG kick down thing is very interesting and highly situational.

So the DSG can very quickly shift from an odd to an even gear (or the other way around).
That's cause it just switches over clutches - which is done in fractions of a second including speed matching.
In that case there is no real feel to the gear change - since the clutches disengage and engage simultaneously so there is no moment where the motor is disconnected from the wheels.
The electronics also alter your gas input in that short moment to allow precise speed matching.

However, when you kick down, the sequence of operations is a bit different.

The electronics first check how much throttle you apply.
Then they decide which gear to select.

If the gear needed is in the same gear train as the one you are in, they shift down one gear first like they usually would.
That is rare though.

If the gear is in the other gear train - which is most common, usually 7th down to 4th - the electronics keep your throttle input from going through.
The system takes about half a second to shift that not engaged gear train from the pre-selected gear (6th, usually) to the needed gear (4th).
Then it lets your throttle input go through, starts to disengage the one clutch, let's the engine ramp up a bit and then engages the clutch for the new kick down gear.

There, speed matching isn't done as exactly.
Idea is you just want to get more torque as quickly as possible.
That way is the most time efficient.

Most DSGs have a "Sport" selection. That takes the normal shift rpms, ignores them, and always runs in the lowest gear possible (so only shifts once you are close to redline).
After the kick down, as long as you do not reduce throttle, it will behave as if you are in that mode - until you reduce throttle, then it starts to shift up through the gears like it usually would.

DSGs actually came from racing though.
Any F1 car has the equivalent of a dual clutch transmission.
Just that they aren't as automated.

Main advantage is that you can shift gears very quickly (F1 cars take less than a tenth of a second to shift) and that as long as the car is moving there is no point where there is no torque going to the wheels - there is always a gear engaged.

 

[foraloysius]

I can imagine that your friend's mother had that feeling. But actually you have influence on the shifting by the throttle just like every other automatic transmission. It's not that the system is bad at shifting, it just shifts more unexpected than when you do it yourself. When you shift yourself you know exactly what is going to happen, with a transmission like in a Smart you don't anticipate as much on it as in a manual.

One other thing is that you can't go full speed ahead immediately, you just have to make sure the car is in gear. If you do it right away and the first gear isn't engaged yet, the engine will make a lot of noise and nothing will happen, or at least at the beginning. Then it goes full speed ahead with a lot of noise, maybe she experienced that.