Late upshift cuases forward surge - Toyota RAV4 Forums
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#1 (permalink) Old 01-22-2013, 04:05 PM
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Late upshift cuases forward surge

Has this happened to you.

The RAV seems to like to hold on to lower gears while travleing downhill. The transmission has an overdrive or half gear. Often when going down a long decent the car seems to hold onto or shift into a lower gear. I noticed by watching the speed and the RPMs. If while travling on the same downgrade and accerlate breifly, the car will shift into top gear. I found this feature quite nice in controling your speed on a long decend without having to downshift a whole gear.

However occcasionally it seems like the car take a second or two to decide if it will hold the gear or upshift. When it does upshift, the sudden release of engine braking makes it feel as if the car lurches forward. Odd sensation. This has happened to me a low speed in the parking lots too.

wonder if other Toyota cars do this. And could this be mistaken for "runaway accleration".

2012 4wd i4 3rd row
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#2 (permalink) Old 01-22-2013, 07:44 PM
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This is the logic built into a lot of vehicles. It was in our 2002 Honda Odyssey that preceded our Rav and worked in the same way. If, when coasting downhill, you are on the brake for more than three or four seconds, the ECU will direct change to a lower gear to assist with keeping vehicle speed in check. It then takes a few seconds back on the gas before it upshifts again, and that's to eliminate the hunting back and forth between this braking assist mode and regular driving mode.

The runaway acceleration is almost certainly due to carpet entrapment or user error/driver ineptitude. There is no passenger car today that has an engine powerful enough to overcome the brakes, and that includes the 1200 HP Veyron. In any vehicle that gets into a full throttle mode, using the brakes fully in one continuous hard application will stop any vehicle, of that there is no doubt.

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#3 (permalink) Old 01-22-2013, 08:25 PM
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if I take my foot off the throttle when approaching a stop light at some distance away I get a feeling like a light bump from the rear as it eventually slows to 30MPH. This happened with the original and the replacement transmission. Is this what you're referring to?

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#4 (permalink) Old 01-23-2013, 12:54 PM
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Originally Posted by RTexasF View Post
if I take my foot off the throttle when approaching a stop light at some distance away I get a feeling like a light bump from the rear as it eventually slows to 30MPH. This happened with the original and the replacement transmission. Is this what you're referring to?
Exactly!

2012 4wd i4 3rd row
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#5 (permalink) Old 01-23-2013, 02:13 PM
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Quote:
Originally Posted by MrPulldown View Post
Exactly!
You're now describing something else. The "release" you feel at about 30 MPH is the torque converter mechanically unlocking. When it is locked and you are off the throttle, you have engine braking causing the Rav to slow down. Once it unlocks, the Rav is essentially rolling as if it were in neutral, so you feel the lack of engine braking and perceive it as the car surging.

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#6 (permalink) Old 01-24-2013, 08:56 PM
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Quote:
Originally Posted by rav4two View Post
The runaway acceleration is almost certainly due to...user error/driver ineptitude.
Roger that.

I heard the audiotape of the guy in California who called 911 to allege that his Prius was barrelling down the highway at 90 MPH and he had both feet on the brake. The 911 operator asked him if he had tried shifting into neutral. He hesitated for a minute, said "No", paused a few seconds longer then yelled "I'm trying to control the car!"

So he could pick up his phone and dial 911 and carry on a conversation, but he couldn't move his right arm 1 foot and slip the lever into N?

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#7 (permalink) Old 01-25-2013, 10:10 AM
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Originally Posted by MrPulldown View Post
Exactly!
Then it's normal or at least both of our RAVS have done it since day 1 so I consider it normal.

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