CVT trans overdrive operation

Philip · Jul 25, 2010

Not sure if I have a problem, but when I push the overdrive off button at around 40mph the tach goes up to almost 3k rpm. I am use to normal trans that jump 6 or 7 hundred rpm when going to overdrive off.
Is this normal operation of the cvt? I am afraid to use OD off for braking purposes.

TopazM3 · Jul 25, 2010

you don't need to use it for braking purposes. The programming of the CVT senses that you are slowing, especially if you're going downhill and alters the gearing to assist with slowing the car. I live on a large hill and it works every time going down hill.

Philip · Jul 25, 2010

mine does the same unless I keep the gas pedal depressed slightly. I guess the OD button serves no real purpose

9495 · Jul 26, 2010

Well, that's not entirely true. OD On/Off COULD be useful on a CVT. The whole point of overdrive is that the ratio is inverted, usually on the top 1 or two gears of a tranny so that the drive gear is larger than the driven gear, right?

On a CVT, this could/should work in the same way meaning that the ration between the two pulleys would never go past 1:1, thereby increasing the RPMs at higher speeds. This would be useful in the same way that OD OFF is useful in a regular auto tranny when going down a grade or something to provide a bit of engine braking.

My understanding is that the big benefit of a CVT is that you get MORE of an "overdrive" range than on a conventional tranny, so it would follow that you might notice more of a jump in RPMs when turning off the Overdrive.

HOWEVER, I'm sure the term "overdrive" has about 300 different meanings these days, so who knows how the Nissan engineers really designed it to behave when you have the OD Off button engaged. (by the way, the first gen MOs didn't have overdrive off options)

njjoe · Jul 26, 2010

Corin said:
Well, that's not entirely true. OD On/Off COULD be useful on a CVT. The whole point of overdrive is that the ratio is inverted, usually on the top 1 or two gears of a tranny so that the drive gear is larger than the driven gear, right?

On a CVT, this could/should work in the same way meaning that the ration between the two pulleys would never go past 1:1, thereby increasing the RPMs at higher speeds. This would be useful in the same way that OD OFF is useful in a regular auto tranny when going down a grade or something to provide a bit of engine braking.

The TCM is programmed to do all this automatically. If you are towing a trailer the TCM will adjust the ratio to ensure the engine is not lugging. If you are descending a steep grade the TCM will adjust the ratio to increase engine breaking and the engine's computer will shut down the injectors to enhance the effect.

People have become conditioned to the action and feel of a conventional automatic transmission. The CVT's seamless flow of power is disconcerting to many. I am sure a lot of people who buy the MO have no clue what a CVT is, but they know the older Honda or Chevy they traded-in for the MO did have an OD button on the shifter, and they damn well want one on their new $35,000 MO.

Personally I believe it is nothing more than a marketing gimmick to give the appearance that the MO is equipped with a conventional auto tranny. I'm not fooled, but I am not the consumer it is targeted at. If it helps them sell more cars without dumbing-down the vehicle too much then that is fine by me.

-njjoe

CVT trans overdrive operation

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