CVT follow-up thread

[AZjeff]

The CVT dislikes thread was interesting and raised a couple of questions for me.

1. Is a CVT more or less complicated with more/less parts that today's 6-9 speed autos? Is there a logical reason they can't be as dependable? Of course Nissan got it wrong at first but thinking about them structurally.

2. Are today's 6-9 speed autos potentially as reliable as the previous gen 4-6 speed autos? It seems like packaging more parts in the same space would make the gears & bearings thinner and possibly not as strong?

There are a number of experienced mechanics in the mob who should be able to give some unbiased answers, then there's the rest of us...

 

[wdn]

You counted 6 speeds twice.

 

[bbhero]

240k miles on my CVT Altima 3.5.

Pretty good I think.

I think the motor and how it is set to run by the computer in combination with the CVT transmission is a big part of this whole equation.

 

[tomcat27]

The cvt on the 6 cyls is a lot stronger unit. Even so there are always Muranos on the rack at the dealer witn the transmissions out. The 6 to 10 speed autos seem fairly reliable. No doubt they are a little pricey to fix.

Cvt has fewer parts but very complex software. And the exact friction is very important.

 

[Number_35]

Good questions! I think the sweet spot for automatics is 5 - 6 speeds. I too worry about the apparent complexity of the > 8-speed transmissions.

As far as CVTs, Nissan may have erred in using too small a transmission in too heavy a vehicle. (Any other old guys with long memories who recall the GM debacle of almost 40 years ago when they were using TH200s [appropriate for Chevettes] in Malibus and BelAirs?)

A CVT is inherently very simple - it seems to me that if they are built well they should last fine.

This may be like the mistrust of disc brakes in the '60s - I have a Popular Science or Popular Mechanics from that era in which the automotive editor debates master mechanic Smokey Yunick over the use of merits of disc vs. drum. CVTs may be the same way - trouble-free and dominant in a decade or so.

But at this point, I prefer a manual transmission when available, and a conventional automatic otherwise.

 

[benjy]

with the high cost of repair or replacement if i were not a die hard shifty guy i would NOT buy a CVT powered vehicle!!

 

[edwardh1]

where does it stop = how about 14 speeds ?????
seems it would be shifting all the time to get into the "right" gear.

 

[clinebarger]

Originally Posted By: AZjeff
The CVT dislikes thread was interesting and raised a couple of questions for me.

1. Is a CVT more or less complicated with more/less parts that today's 6-9 speed autos? Is there a logical reason they can't be as dependable? Of course Nissan got it wrong at first but thinking about them structurally.

2. Are today's 6-9 speed autos potentially as reliable as the previous gen 4-6 speed autos? It seems like packaging more parts in the same space would make the gears & bearings thinner and possibly not as strong?

There are a number of experienced mechanics in the mob who should be able to give some unbiased answers, then there's the rest of us...


1. CVT's have less parts & are far cheaper to manufacture compared to 4 speed automatics made 15 years ago. Then again we would need to get into specific units.

2. Too many design variables to answer this question, Not every added ratio requires adding a Clutch Drum/Band & Planetary. For example....The Allison 1000 5 speed became a 6 speed with nothing more than a valve body & software changes.

 

[sloinker]

We had CVT gearboxes on a steam turbine driven line shaft at a paper mill I worked at some years ago. They were not trouble free but we are talking a few thousand horsepower. They did the job but we ended up retrofitting the paper machine with DC drives and got rid of the line shaft mostly due to the steam being needed for a new turbine generator.

 

[AZjeff]

Originally Posted By: wdn
You counted 6 speeds twice.


Yeah I know. It seemed to me 6 speeds were the high for a while then it went to 8/9 so 6 may be a delineating number..or not.

 

[edyvw]

Originally Posted By: edwardh1
where does it stop = how about 14 speeds ?????
seems it would be shifting all the time to get into the "right" gear.

BMW decided not to put more then 8 speed transmission on longitudinal models.
They also wanted to stick to 8 speed Aisin (Toyota) on their transverse engine models but considering issues with that transmission that Toyota and some manufacturers have, BMW it seems will move to 9 speed ZF.
GM/Ford will stay at 10, MB at 9.
It is hard to justify more speeds and there will be less investment in that considering push toward EV.

 

[Oildudeny]

I haven't found a cvt that makes me happy, though I only had 4 cyl cvt vehicles. a friend had a maxima which drove much differently actually that car was quite powerful

 

[Oildudeny]

6 spd is plenty of ratios for power and economy

 

[JTK]

Originally Posted By: Oildudeny
I haven't found a cvt that makes me happy, though I only had 4 cyl cvt vehicles. a friend had a maxima which drove much differently actually that car was quite powerful


Ridiculous I know, but same with our Nissan Quest. It will light the tires right up if you stomp on it. VERY different feel and drive to it than my inlaw's 2016 Nissan Rogue.

To me, that's the biggest part of it. Lots of CVTs, especially the ones folks complain about are installed in vehicles that are small, underpowered and cheap to begin with. For the most part they'd still suck with a 4,5,6 speed auto in them anyway.

Like said, I don't buy the "expense to fix" argument at all. What transmission these days isn't $6000+ to replace when something catastrophic with it happens? My personal opinion on them is, I don't have a lot of faith in ANY of them, regardless of being CVT/conventional auto.

 

[edyvw]

Originally Posted By: JTK
Originally Posted By: Oildudeny
I haven't found a cvt that makes me happy, though I only had 4 cyl cvt vehicles. a friend had a maxima which drove much differently actually that car was quite powerful


Ridiculous I know, but same with our Nissan Quest. It will light the tires right up if you stomp on it. VERY different feel and drive to it than my inlaw's 2016 Nissan Rogue.

To me, that's the biggest part of it. Lots of CVTs, especially the ones folks complain about are installed in vehicles that are small, underpowered and cheap to begin with. For the most part they'd still suck with a 4,5,6 speed auto in them anyway.

Like said, I don't buy the "expense to fix" argument at all. What transmission these days isn't $6000+ to replace when something catastrophic with it happens? My personal opinion on them is, I don't have a lot of faith in ANY of them, regardless of being CVT/conventional auto.

I would say Quest light tires due to soft suspension. Those vans in general will light tires, CVT or not. Toyota, Honda etc. with huge torque steer etc.
For example Toyota Sienna will get better time with AWD although it has 200lbs in addition. Reason? Wheel spin on FWD.