CVT Transmissions

[Witchfire]

If anyone has any questions concerning Nissan/Jatco CVT's (i.e.- Nissan Murano and Dodge Caliber), I will be happy to share what I know about them. I currently work with the company that manufactures and services them, and have a number of years of experience with them.

[Remonster]

Maybe you could make a guide on them? Sort of what Spooked Junglist has done here: http://carforum.net/showthread.php?p=71#post71

[Witchfire]

I'll tell you the truth on that score... I could pretty easily do it, but I'd be more than a little afraid of my company finding it. Most of the tech is proprietary to us, and I know a lot of it is considered a 'company secret'. I know the units inside & out, but I couldn't tell you what would be a disclosure of confidential material. It may sound chicken-*****, but it's my job we're talking about... know what I mean?

[Remonster]

Absolutely, I was thinking more along the lines of explaining the basics of how they work and the like, no one wants to hear your company secrets lol :p

[PeDrO305]

I heard something about that...... On the newer Altimas right? I heard it *sounds* like one BIG gear.

[SpookedJunglist]

Well you know that all factory shop manuals are meant to be public so that any shop can perform repairs on any car. CVT is nothing new it has been on the super economy civics since the mid 90's. I remember how they work. It is a computer controlled set of pulleys on the engine side of the transmission connected to another pulley that is the main drive shaft that drives the wheels.

The tricky part is the computer controlling it. The tranny itself is rather simple. Each pully is made up of two cones on a shaft; the shaft is regulated via a computer to make sure that the V belt connecting them does not get loose. the diameter of the pulley on either side changes creating gear ratios. The funny thing is that there are no gears. Like I said simple stuff. I found a picture on howstuffworks. I did not know that Leonarda Davinci invented it in 1490:eek:. Dude that guy must have been abducted by aliens or something.

http://static.howstuffworks.com/gif/cvt-14.gif

Please let us know if nissans use a different system. I find it funny that the how stuff works page does not mention the mid 90s civic:(

More info here (http://auto.howstuffworks.com/cvt.htm)

[apavlov13]

I think some citroens in europe had that without any computers. A couple springs here and there, and the ratio is "automatically" selected bades on the load. The higher the load, the lower the ratio.

[SpookedJunglist]

Yeah they could be controlled by cintrifugal force to move springs and adjust the pullys that way. I think it has been done that way. I think now they use throttle position to decide if it really needs to beaccelerating as fast as possible. if you arent trying to go fast you can save gas with a computer controlling it. But who cares Gas gets cheaper and cheaper every day :(

[The Duke]

Has any of you ever seen a torq converter in a snowmobile, same principle as the above graphic but they wern't computer controled.

[Witchfire]

Well you know that all factory shop manuals are meant to be public so that any shop can perform repairs on any car. CVT is nothing new it has been on the super economy civics since the mid 90's. I remember how they work. It is a computer controlled set of pulleys on the engine side of the transmission connected to another pulley that is the main drive shaft that drives the wheels.

The tricky part is the computer controlling it. The tranny itself is rather simple. Each pully is made up of two cones on a shaft; the shaft is regulated via a computer to make sure that the V belt connecting them does not get loose. the diameter of the pulley on either side changes creating gear ratios. The funny thing is that there are no gears. Like I said simple stuff. I found a picture on howstuffworks. I did not know that Leonarda Davinci invented it in 1490:eek:. Dude that guy must have been abducted by aliens or something.

http://static.howstuffworks.com/gif/cvt-14.gif

Please let us know if nissans use a different system. I find it funny that the how stuff works page does not mention the mid 90s civic:(

More info here (http://auto.howstuffworks.com/cvt.htm)


Right on the money on how it works, Spooked... Shop manuals aren't something we deal with on this end. The CVTs we supply have no user or dealer servicable parts, hence why I'm reluctant to post any of it.

The comment about the Altima is correct. The CVT used in the Altima is an updated version of the unit used in the Nissan Murano. There was a big enough list of problems with that unit that, once compiled, they decided on a complete revision, rather than a few updates at a time.

You're right about the basic operation of the unit, but some of the specifics are left out from most of the publicly available info. One basic thing is that the main line pressure in the CVTs used in the Murano & Altima can easliy exceed 1000psi, due to the nature of the belt drive & the amount of force necessary to hold the belt in position without allowing slippage. This is a great thing from a belt-to-pulley standpoint, but is absolute hell on a control valve unit. A very small amount of contamination in the fluid can score the valves enough to cause major problems in pressure control.

Machining the valvebodies is also a major concern. We've had problems in the past where the clearance was very slightly over specs, and it allows the pressure from the opposing side of the valve to bleed to the holding side & overcome it. At the aforementioned pressures involved, you can imagine the havok this can cause.

You were slightly mistaken in that there is a gearset involved in all CVTs. There is a single planetary set used to allow a reverse gear, and to lower the actual applied ratio.

The belt we've been referring to is a german manufactured piece consisting of multiple steel rings on each side holding a few hundred individual steel 'elements' in place.

There is no actual metal to metal contact between the belt & the pulley surfaces, because of the unique fluid CVTs use, there is always an almost microscopic film of oil between them. Many of the returns we've received were because of some uninformed individual or establishment performing a fluid change and using one of the industry standard Type F or Dextron types of fluid. Neither will hold film the required film strength, nor stand up to the pressures involved very long before breaking down.

[cdub998]

I have a question about the CVT's. I just bought a caliber and needed to know about changing the fluid? How often and can I do it myself or is it too involved?

[Pinhead]

http://static.howstuffworks.com/gif/cvt-14.gif
More info here (http://auto.howstuffworks.com/cvt.htm)

OMG :D

We have those on our Gleaner combines!! THEY WERE MADE IN THE '50s!!!!

:p

I've noticed a LOT of "new" technology being advertised that "we've" (farmers) have had for 60 years! :eek:

[SpookedJunglist]

OMG :D

We have those on our Gleaner combines!! THEY WERE MADE IN THE '50s!!!!

:p

I've noticed a LOT of "new" technology being advertised that "we've" (farmers) have had for 60 years! :eek:

Leonarda Davinci Designed it. I looked it up:eek:

[Witchfire]

I have a question about the CVT's. I just bought a caliber and needed to know about changing the fluid? How often and can I do it myself or is it too involved?

You should NEVER need to change the fluid in your CVT. It is a lifetime fill, and should not need any replacement of fluid unless the unit needs work done on it. Moreover, CVTs use a VERY special fluid, and CANNOT be mixed with any other type or brand.

[Pinhead]

Leonarda Davinci Designed it. I looked it up :eek:

Heh even better!

[SpookedJunglist]

Heh even better!

I thought that was funny. That guy must have been abducted by aliens or something. He was the man!

[Neon7caliber0]

New here I was reading the forum about the cvt transmisson and the caliber. I was wondering how good the caliber really is. Own a driving school and have neons to teach people to drive and its time to replace one car and I was thinking about the caliber. But what I have been reading I can use somemore advice about the car.

[ancarte]

I was wondering what would be involved in replacing my existing transmission with a JATCO cvt transmission on a rear wheel drive vehicle

Would this be possible and would you know what kind of work would be involved to carry out such a project.