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Guest Message by DevFuse
 

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Crazy idea!


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9 replies to this topic

#1 1 Lucky Texan

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Posted 12 August 2013 - 10:24 AM

On another forum, someone asked how fast the CVT transmission could go in reverse.

That made me have the crazy idea, suppose someone could 'hack' the CVT to run its full gear range in reverse! Yeah, maybe some external fluid pumping would be needed? And custom electronics (or firmware?) etc. But, it make for interesting swaps and customized vehicle!

has it been done? who's gonna be the first to do it?

Edited by 1 Lucky Texan, 14 September 2013 - 12:30 PM.


#2 ivans imports

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Posted 12 August 2013 - 10:35 AM

still has a crown / pinion they are not meant to run backwards powerd



#3 1 Lucky Texan

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Posted 12 August 2013 - 10:43 AM

no question the engineering is for forward, dunno how much running backwards would tear-up the internals. Would it cut the unit's lifespan down to days? in half? 10%?

#4 presslab

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Posted 12 August 2013 - 12:14 PM

Interesting idea.

 

Reverse is possible because of a planetary gearset aft of the chain.  Going forward this gearset is locked up and has no ratio effect.  In reverse this unlocks allowing the sun gear to spin in reverse.  What this means though is that reverse has a different gear ratio than forward.  I don't know what this ratio is (maybe 150%) but it's something to consider - basically it means there is less torque multiplication available in reverse.  Also I'm not sure if the planetary gearset is durable enough for continuous use.

 

20384d1311213130-2011-ob-cvt-reverse-pow

 

There are people running entire Audi transaxles in reverse.  While a R&P does have drive/coast directions, the Subaru transaxle already "drives" off the "coast" side so I don't believe that's the issue.  The R&P is only designed for the front drive wheels which will slip much easier than the rear wheels.  If driving in reverse (or mounting the transaxle in reverse) the peak loads it sees will be much higher.  In drag racing the front housing has been known to break on the 4EAT.  This implies that the gears are strong enough, but the housing is not.

 

That said, I think as long as the torque is kept below the point that will distort/crack the housing, it should have a long service life.


Edited by presslab, 12 August 2013 - 12:15 PM.


#5 1 Lucky Texan

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Posted 12 August 2013 - 01:03 PM

interesting - looks like that planetary reduction could be 'locked' with some kind of drop in?

#6 Uberoo

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Posted 05 September 2013 - 02:00 AM

thats just a regular 4EAT not the CVT. A CVT doesn't have the tradional sun/planet gears a normal automatic has.



#7 ivans imports

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Posted 05 September 2013 - 09:17 AM

I most defanatly smoked the backside of crown / pinion and only did a 150 backwards pass mind you 300+ hp with nos and 31 paddle tires. It dident break just melted smeared and striped. I a'm still not a beliver of backwards runing diff



#8 presslab

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Posted 06 September 2013 - 10:18 PM

thats just a regular 4EAT not the CVT. A CVT doesn't have the tradional sun/planet gears a normal automatic has.

 

You're sure about that?  Must be, otherwise you wouldn't have posted it...



#9 Gloyale

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Posted 14 September 2013 - 10:49 AM

thats just a regular 4EAT not the CVT. A CVT doesn't have the tradional sun/planet gears a normal automatic has.

 

That's definately not a 4EAT.  Maybe a 5EAT, never seen one apar.t

 

The 4EAT you cannot remove or even see the plantary sets with the rear housing removed.

 

I think that may be the only set of gears in there, and they are used just for reversing like press suggested.



#10 Uberoo

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Posted 21 September 2013 - 06:16 PM

My bad I was under normal automatics had the planetary gears,I suppose its not that far of a stretch for a CVT to have a planetary gear for reversing duties.Normal automatics use them like that that.






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