Mrs. L.A. was on a steep hill in her 2010 RAV4 yesterday. After visiting a patient, she pointed the front of her car downhill and went slowly down. It was only upon reaching the bottom of the hill, she discovered that she’d been in reverse all the way down. The car functioned normally the rest of the day, and apparently she had no trouble with it today. But she’s concerned.
I know that automatic transmissions are sometimes called ‘slush boxes’ because they have a torque converter, which is a fluid coupling between the engine and the transmission, instead of a mechanical connection. I’m guessing that gravity was greater than the force of the fluid connection (I presume she was not stepping on the accelerator pedal since she was on a steep hill), so the car moved forward even though the engine and transmission were trying to make it go backward.
What are the odds that she damaged something, and what would be the repair?
Was the car running? With automatic transmission? Weird then.
I imagine if you did that too often and too fast you might break something; but I suspect the worst risk would be pumping something the wrong way in the transmission and making a seal leak… However, I don’t really know that much about transmissions so it’s a semi-wild guess.
I don’t see how this could damage anything.
The torque converter is designed to slip - that’s how the car can be in gear and not moving (like, at a stop light).
Forcing the torque converter to run backwards is just an extreme case of it being stalled.
I’m assuming that the comments so far are true, because I have no reason to doubt them. In that case, this is something that car manufacturers warn against because it will soon cause excessive transmission wear, but is not a truly dangerous activity.
The risk is probably isolated overheating of an internal component (and cooking the fluid… but dubious at best), which is not immediately manifested during the operation or even shortly thereafter. I don’t think that risk was very great, but pressure and temps did probably rise internally. So ‘damage’ is such a loose word, because parts are designed to ‘wear’ (be damaged gradually over time, which is variable).
People do much worse in daily driving of their automatics and manuals, so if it was a minute or two and she slipped the trans at idle the whole way down, I can’t imagine recommending anything more than a fluid check/change.
Slush boxes don’t grenade, in this type of scenario, because there is no mechanical connection to snap/bend/etc, but heat and pressure can’t shorten service life.
You don’t say how slowly she was going. But some automatic transmissions have a feature that will pop them out of Reverse if they are moving more than 5 mi/hr forward. To protect the transmission, I believe. Possibly this had happened, and internally the transmission was in neutral, even though the indicator level still showed R.
If its the traditional automatic thats quite alright. Its a slush box with the torque converter.
If its a automatic-clutch (single or dual) , or variable transmission… then the computer put it in neutral and refused to engage until it was moving in the appropriate direction.
For ‘slush-boxes’ it’s overheating that is the problem. The same reason you shouldn’t tow one more than a short distance without disconnecting the prop shaft.
The reason you don’t tow a automatic with wheels on the ground is because the oil pump for the tranny fluid is on the engine side and requires engine rotation to operate, so no engine rotation, no fluid circulation.
No, nothing bad will happen. The transmission will be just fine. Slamming it into ‘R’ while moving forward could cause issues but not if coasting down a hill with it engaged. If you want to check it, just go for a drive and cycle through each gear manually and make sure they engage in a timely fashion (under 1 second). If they don’t engage instantly its likely just older transmission fluid. If they do not engage at all, then there is a problem.
I didn’t receive a ‘Help me!’ call, so I assume Mrs. L.A.'s car is functioning. She has the oil changed regularly. I’ll suggest she have them check the transmission fluid next time she goes in.