CVT Transmission Discussion

[dakboy]

Originally posted by rockhopjohn
I don't know what kind of lube the tranny uses, but Subaru indicates it is a lifetime fluid for the average driver, but recommend replacement at 24,588 miles (what an odd number) for those who haul heavy loads, or tow.

That's just short of 40,000 KM (within 500 KM or so).

[CNY_Dave]

Originally posted by bhayden
I didn't realize they'd done away with the torque converter with the CVT. One nice thing about a torque converter is it does easy shock on the drive train when doing things like trailer towing. And speaking of severe duty like trailer towing, if the CVT isn't up to the power of the H6 or the turbo doesn't that make you wonder if the CVT is a bit marginal for the application?

Without a torque converter what gives when the car is "in gear" and you're stopped?

The Subaru design uses a chain but near as I can tell it really functions more like a belt in that it rides on tapered pulleys rather than sprocket arrangement. I'd be concerned with the wear pattern. Wouldn't long amounts of time at one speed (e.g. freeway driving) tend to put a groove in the pulley halves?

Do these babies use ATF or a manual gear lube?

Are they still using the Active Drive AWD system? If so is the section in the tail shaft basically the same as the conventional automatics?

How do they back up? Is that a fixed gear or is this thing capable of 70mph in reverse

Is it a 'pulling' belt (normal arrangement) or is it a 'pushing' belt?

I remember a CVT that was a belt made of flat metal plates strung on steel wire- the driving pulley pushed the belt instead of pulling it.


Dave

[rockhopjohn]

Originally posted by dakboy
That's just short of 40,000 KM (within 500 KM or so).

Ahh, I think you are right, I misquoted the number, it should be 24,855 mi, and that rounds to exactly 40000 km.

[bhayden]

Originally posted by CNY_Dave


Is it a 'pulling' belt (normal arrangement) or is it a 'pushing' belt?

I remember a CVT that was a belt made of flat metal plates strung on steel wire- the driving pulley pushed the belt instead of pulling it.


Dave

I think what you are describing was known as a metal belt. Subaru is actually using a chain; linked together vs "woven". I would have to think most of the force is from the chain in tension (pulling chain). A chain or belt wants to buckle in compression plus I think it would want to ride up out of the vee pulley which would mean even stronger clamping force.

[rockhopjohn]

One thing that we can't see in any of the diagrams is the actually shape of that drive chain. I am betting that it is a V shape, it certainly wouldn't make any sense for it to be a flat chain with that tapered pulley arrangement.

[CNY_Dave]

Originally posted by bhayden

I think what you are describing was known as a metal belt. Subaru is actually using a chain; linked together vs "woven". I would have to think most of the force is from the chain in tension (pulling chain). A chain or belt wants to buckle in compression plus I think it would want to ride up out of the vee pulley which would mean even stronger clamping force.

Now that I think of it, it was actually the subaru justy that used the metal-plate pushbelt CVT.

The nissan murano CVT is also a pushbelt CVT (now that I do a bit of googling).

Essentially, if it's a bunch of metal plates held together with metal banding, it's a push belt. Anything woven or with links sounds like it's have to be a pull-belt.

Typical pushbelt:



For those that love TMI:
http://www.bosch.nl/content/language...lley_level.pdf
http://www.bosch.nl/content/language...robustness.pdf

Dave

[nipper]

yes the push belt was a subaru patented design, it really was a smart way of doing it.

On projected maint and life
http://blogs.thecarconnection.com/ma...ntenance-costs

Now look at this picture
http://www.subaru.com/engineering/transmission.html

Pic from the autoshow (large poics I took)

http://www.flickr.com/photos/nipperd...7616957539400/

http://www.flickr.com/photos/nipperd...7616957539400/

Really goos chain pic
http://www.flickr.com/photos/nipperd...7616957539400/

http://www.flickr.com/photos/nipperd...7616957539400/

The chain has teeth both pins that hold the chain together. They most likely work together to bite the drums.. As with any transmission, as long as the teeth dont slip, there should be no issue that i can see. The hyd fluid aould be acting like cutting lubricant, keeping the teeth sharp. Unlike cutting metal, you are never really going over the same spot for any length of time to do damage. So once again subaru is using the compression model to drive the car. We think of chains that wtretch by the links elongating. The stress is equally split on the link pins and the links.

Will it last? I dont know. Can it, quite possibly.

[rockhopjohn]

All those galleries on Flickr are set to private.

[nipper]

Originally posted by rockhopjohn
All those galleries on Flickr are set to private.

How odd, they shouldnt be...

[nipper]

http://farm4.static.flickr.com/3356/...5f9020bd_o.jpg
http://farm4.static.flickr.com/3361/...e169bc1e_o.jpg


http://farm4.static.flickr.com/3621/...058d39f5_o.jpg
http://farm4.static.flickr.com/3623/...1bb72273_o.jpg


in the same order as posted, lets try that. If your a flickr member you can see them blown up. i can post one blown up pic here, but it is very large, but does show the chain contact points very well.

So if anyone wants to see it let me know, i just am hesitant to post a big pic like that.


nipper