Is this some weird CVT behavior?

I drove into my driveway the other day (that being the logical thing to do in a driveway :-)), and forgot to put my Outback into park before picking up pen and paper to log my mileage. I must have taken my foot off the brake, because the next thing I noticed was the car slowly rolling backwards down the driveway.

The next day I tried just the opposite: I backed in the driveway, left the car in reverse, and took my foot off the brake. It started rolling forward.

Call me old-fashioned, but putting a car into a forward gear used to mean that it couldn't go backwards, and vice versa. Is this "fluidity" in the Outback the result of the no-gears design of a CVT transmission? If so, it's a bit unnerving.

Patty

Reply to
Patty Winter
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Don't know but interested in knowing about how CVT behaves as it might be option for my next Subaru.

Saw another one the other day where my brothers Outback's automatic transmission had a manual mode where you could shift with buttons on the steering column. Don't know what advantages are.

I live in a hilly area and wonder what best option might be.

Reply to
Frank

So is your driveway inclined even if just a little? Let's assume the driveway is inclined which is typical to allow runoff, and it is inclined upward from road to your garage.

You drive forward into the driveway and presumably leave the transmission engaged (foward). The car is tilted up on the front. You take your foot off the brake. The car starts to reverse down the incline. This is what happens when a car is in neutral: it starts to roll in the direction on the incline.

You drive backward into the driveway and presumably leave the transmission engaged (backward). The car is tilted up on the rear. You take your foot off the brake. Thar starts to forward down the same incline of the driveway. This is what happened when a card is in neutral: it starts to roll in the direction of the incline.

So it looks like the CVT is going into neutral when there is no load on the engine. Isn't that how it's supposed to work? If it were still engaged when it should be in neutral then more fuel is being consumed.

You're used to an engine that remains engaged through the transmission so there is always some torque in the direction for the currently selected gear. In the old automatic, you putting your foot on the brake did not disengage the engine so you lifting your foot from the brake would have your car start moving in whatever direction (forward or reverse) you had put the transmission. The "at rest" torque you're used to with a traditional tranny isn't there with CVT. When at rest (no load), CVT has put itself in neutral so when you lift your foot off the brake then the car will start to roll in whichever direction the car is tilted.

The point of the CVT is to reduce fuel consumption hence raising fuel efficiency. When at rest, leaving the engine engaged means leaving a load on it which mean more fuel gets consumed. You aren't used to "idle neutral" which shifts the tranny into neutral when the car is stopped and the brakes are applied. This reduces drag (load) on the engine to increase fuel efficiency. I've read about Mitsubishi with "CVT with Neutral Logic". Looks like Subaru employs the same scheme.

What do you think would happen if you drove into your driveway (using either forward or reverse to pull in), used the brakes to stop the car, manually put the car in neutral gear (whether a traditional automatic or CVT), and then released the brake? Yep, the car would start rolling down the hill because, well, it's in neutral.

There are many types of CVT. The manufacturers seem to keep secret how theirs work. There are what are called "neutral transmissions". When the load on the engine is minimal, like sitting at a stop or coasting down a hill, the tranny goes into neutral. With a traditional tranny, you should rev the engine to get its effective RPM to match your speed to reduce engine braking effect when engaging the tranny out of neutral. With a CVT, it can alter the tranny gearing while staying in neutral (to maintain the smooth driving experience). When coasting, and because the car may accelerate to a speed above what you want, you may have to apply the brakes to slow you down hence more brake wear. So they give you the option to use manual shifting to let you control the engine braking.

I haven't yet had a car with CVT but what you describe sure sounds like "idle neutral" in an "idle transmission". Your brakes (foot or parking) are supposed to keep you at a stop so why bothering loading the engine to eat up more fuel when you're at a stop?

I'm waiting until CVT has more history to decide if I want one. My old '92 Subaru Legacy is just now having a tranny problem (but suspect the shop that did the tranny flush put in the wrong fluid). I have a couple later Subies but still no CVT in them. I'd like a CVT-equipped Subie to last as long as my others so longevitiy is an issue. Ford's Freestyle CVT made by Jatco

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had sudden unexpected breakdowns while driving. Nissan's have been critized as less reliable that standard automatic transmissions. There is also a difference in driving feel and control, especially for car enthusiasts (but the same is almost always expressed between automatic and manual transmissions). CVTs are more expensive to buy and also to maintain or repair than a standard automatic. CVTs make more noise on startup and when accelerating. While CVTs can rev the engine to match belt/chain speed in the CVT for supposedly smooth shifting in or out of neutral, users have complained of noises similar to clutch slipping in a manual tranny. Some CVTs are still a bit jerky on acceleration so they're no better than an automatic. Some users have complained about an abrupt jerk when coming to a stop (perhaps due to the "idle neutral" feaure). Because users are still accustomed to change in engine speed when changing gears but which is absent for a [supposedly] smooth shifting CVT, paddle shifters are added on the steering wheel to simulate or override gear changes. To me, for now, CVTs are relegated to the gizmo category: nice if you're willing to pay for it but not necessary.

Reply to
VanguardLH

I own a 2014 2.5i Subaru Forester with CVT. I have not noticed it going into a neutral condition when stopped on an inc line while in gear.

I have over 20k miles on my unit, too few to comment on longevity or reliab ility at this point. Compared to my 2002 Forester with automatic though, th e CVT is smoother, and quieter than the automatic, and can wring far more o ut of the 2.5L boxer performance-wise.

There is supposedly a fuel economy boost going with the CVT. The 2014 Fores ter with CVT is rated at 32 MPG highway (which I do get), and the manual is rated at 29 MPG. I put on about 25k miles/year, so with the cost of gas ar ound here, I can save nearly $300/year in gas compared to the auto.

Sincerely, Duane

Reply to
TheSeeker

Apparently so. This is the first CVT, so I wasn't aware that CVTs had this behavior.

I don't think there's a lot of fuel being consumed when the engine is off, but I could be wrong...

Well, they're the only type of automatic transmission that Subaru offers on Outbacks, so I didn't have any choice.

Patty

Reply to
Patty Winter
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You don't even have to put it in manual mode. You can shift the car even when it's in drive.

Patty

Reply to
Patty Winter

A CVT, unlike an automatic, does not use a torque converter. When you step on the gas it shifts the sheaves to transmit power. And unlike a standard trans, it does not "engage" the gears with the engine shut off - so engine running at idle or shut off, with the gear shidt in drive or reverse, there is nothing stopping the car from rolling away.

Reply to
clare

Thanks, that's what I figured was happening. Well, good to know before it happens on a steeper slope!

Patty

Reply to
Patty Winter

Reread your starting post. Where did you say anything about the running state of the engine?

Is your driveway inclined? If so, what happens when you drive the car to a stop by applying brakes, stop the engine, put into neutral, and then release the brakes?

Even with automatic or manual transmissions, it is bad practice to use only the engine to keep a parked car in its place. You brake to a stop, turn the wheels in the correct direction (straight ahead if flat, away from curb for uphill, or towards curb for downhill), put the tranny in first or reverse for a manual or in Park for automatic (the later usually required using a lockout on the key), and then apply the parking brake. It's called a *parking* brake for a reason. I don't recall any method of parking that doesn't end with using the parking brake.

In fact, if you get in the habit of not using the parking brake and just the compression in the engine's cylinders, you may one day need that parking brake but pulling on it breaks the cable. If not moved, the cable can rust in place. There's no continued lubrication of the cable after manufacture. So keep using the parking brake to move the cable to make sure it doesn't rust in place.

I know a lot of folks that become accustomed to using the automatic transmission's parking pawl to keep their car in place when parking; see

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That it works on shallow inclines doesn't obviate it's a dumb way to park. A manual tranny doesn't have a parking pawl so the user would be relying on the clutch and engine compression to keep the car in place when parked. Clutches wear and slip. Parking pawls slip out or break and they rely on engine braking, too. I've seen many times when users have gotten into the habit of using the parking brake but apply it at the wrong time. You stop using the brakes, pull the parking brake handle, and then put the automatic into park. That reduces strain on the pawl and tranny. It doesn't take a big smack of someone hitting your car in the parking lot for the pawl to brake, you not using the parking brake, and finding your car somewhere else than where you originally parked it. Probably the biggest reasons drivers don't properly use the parking brake is they are too lazy, the pawl has been working so far, or they drove the car one day after forgetting to release the parking brake and smelled the burnt brakes and didn't want to do that again (they don't bother looking at the dash to notice the Parking brake warning light). That your car started rolling after you supposedly "parked it" shows you aren't parking properly.

Reply to
VanguardLH

In standard automatic transmissions, there was a parking pawl in the tranny that would keep the car in place while parked. Putting it in "Park" engaged the pawl. It is very bad practice to use the pawl to keep the car in place. It is not designed to prevent movement of the weight of the vehicle yet many drivers get lazy in relying on it to "park" their car even on an incline. You said you put the tranny in Park (but didn't mention stopping the engine). I haven't researched to see if CVT transmissions include the use of a park pawl. Your scenario indicates there is no such pawl.

The pawl, even when present, is not designed to keep the entire weight of the car locked into a parking position. It is a ignorant and lazy practice by drivers of automatic transmissions. Parking on an incline or getting bumped or pushed by another car can break the pawl inside the tranny causing more severe problems (besides the car smashing into something when the pawl wasn't there to block movement).

You got caught using you old bad habit with an automatic: using the parking pawl (Park), tranny, and engine to keep the car from moving while parked. Every recommended parking procedure ends with or includes use of the parking brake. Lots of drivers don't use the parking brake. Well, you can't teach everyone how to properly park their car. Those that do use the parking brake and have automatics usually apply the parking brake too early (i.e., after putting the tranny in Park and therafter leaving stress on the pawl when engaging the parking brake afterward).

Now that you have a CVT, perhaps you'll start employing the parking brake like you were supposed to before when you had an automatic. When parking, you should get accustomed to hearing that zip noise when pulling up on the parking brake. In some locales, you can get ticketed if it can be seen the parking brake lever is down in a parked car because you didn't properly park your vehicle. It's a cheaper wake-up call then having to get your transmission replaced. If the pawl breaks and your car rolls down a hill to smash into another car and it is noted that your parking brake was not engaged, well, you didn't properly park so the fault for the accident is all yours.

Reply to
VanguardLH

Cars with automatics work the same way as your Subaru with CVT. Both have a torque converter between the engine and transmission. This allows the slippage you describe and how your car can be at a stop even when the engine is running and in D or R.

Your observation about the an automatic transmission car not being able to slide backwards while in drive is not correct. Given enough of an incline, it will slide alright - even if it's not inclined to. (-:

Reply to
dsi1

The CVT would seem to be the ideal transmission. What's not to like about no gears? I used to have a variable speed drive on my printing press. It used the same kind of setup as on these modern transmission. They worked very well although driving the pulleys on the sides of that V-belt must have created a lot of friction. Anyway, it worked great and I could slowly crank up the speed and print as fast as I dared. Good luck with your transmission.

Reply to
dsi1

If I didn't say that it was off, my apologies.

My first car was a stick shift (as is one of my current cars), so I have always been in the habit of using the parking brake in addition to putting the car in gear (stick shift) or park (automatic). As I mentioned, I got distracted and had not completed my usual parking procedure in this case. My previous Subie would not have started rolling in this case.

Patty

Reply to
Patty Winter

Read the OPs original post. She did NOT put it in park (which she usually does) when it rolled. Same would have happened with an automatic or a standard UNLESS it had hill-holder and she had her foot on the clutch. Some Soobs have hill-holders (forester, for one) - including automatic Outbacks and Legacys

Reply to
clare

I think that you will find that _every_ automatic transmission car has that effect to varying degrees. Old-style torque converter transmissions 'leaked' a good bit of rotational energy -- put the vehicle in Drive on an absolutely flat surface and the vehicle will creep forward; if the car is very old and/or maladjusted the creep might be more of a lurch. Aim the same car up a slight incline and put it in Drive and it may creep forward more slowly and if the incline exactly balances the tendency to creep then the car will not move but if the incline is more steep then the vehicle will invariably roll backwards. What you are experiencing is as normal as normal can be and is the reason that more vehicles are available with hill-hold.

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Reply to
John McGaw

It used to be that in a car with an exposed cable-operated parking brake, water could freeze on the mechanism and prevent the brake from releasing. So it was inadvisable to set the parking brake after driving on a wet winter's day.

I don't know if any modern cars have exposed brake cables.

Reply to
John Varela

Not only that, but wet brake shoes/drums would freeze together and you were going NOWHERE untill a thaw. Same can happen with disk brakes.(caliper parking brake)

Reply to
clare

Yeah, I remember that used to be a major issue in the 70's and 80's, even before I could drive, I remember my father experiencing it in the

70's. And then later I experienced it myself in the 80's.

Those types of brakes also had the problem of rusting out. So I find that if I use the parking brakes all of the time, then it keeps the cable operational, and breaks-up any rust in the system.

Yousuf Khan

Reply to
Yousuf Khan

I think Patty is a guy, in this case. :)

Yousuf Khan

Reply to
Yousuf Khan

A CVT has a torque converter? This is the first I'm hearing of that. I always assumed it just had an automatic clutch pack to disengage the drive during idling.

Yousuf Khan

Reply to
Yousuf Khan

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