Auto box - changing gear without stopping

[Matt_T]

We have a 2008 Honda Accord auto as a family wagon. I think it's a regular torque converter auto.

My darling wife, who is not very sympathetic to cars, has a frustrating habit when manouevering of shoving it in drive whilst still rolling backwards, using the forward drive of the engine and gearbox to slow the reverse to a stop and start going forward.

As someone who is very mechanically sympathetic it pains me, but I usually keep my mouth shut for marital harmony.

Can anyone advise if this is doing any harm to the gearbox? Given she has driven 150,000 miles in it I guess it's farily robust but I'd quite like to mitigate the gearbox breaking.

Edited by Matt_T on Monday 3rd February 21:01

[Robertb]

Advice in the manual of any auto car I’ve ever owned is to stop vehicle before selecting D, P or R (obvs you can go straight between D-1,2,3)

I imagine the box has safeguards but that said I once went from D to P whilst crawling slowly and it made a very dodgy noise!)

[SAS Tom]

In my head it shouldn’t be too disastrous due to the torque converter. Interested to see what the answer is though.

[InitialDave]

After 17 years and 150k, I wouldn't worry about it, she's not going to change, and you know it'll wait until you're the one driving it to actually break anyway.

[hersh]

InitialDave said:

After 17 years and 150k, I wouldn't worry about it, she's not going to change, and you know it'll wait until you're the one driving it to actually break anyway.

Ain't that the truth!

[Sebring440]

InitialDave said:

After 17 years and 150k, I wouldn't worry about it, she's not going to change, and you know it'll wait until you're the one driving it to actually break anyway.

Good advice.

But it gave him a good excuse to start a new thread on PH.

And when it does eventually break, he'll be straight onto Honda claiming the gearbox is not fit for purpose.

[CraigyMc]

If it's a regular torque converter, then it'll not cause damage.

She's just shearing the hydraulic fluid in the torque converter a bit more than normal, but that's no different than starting the car moving up a hill or towing a load.

[Decky_Q]

If she does it quickly it should be fine, but the advise is to stop because you go through park and there is a locking pawl on the gearbox for park, if shes got the nack of doing it without letting it engage then fine (or the tip is already broken off many miles ago)

[Krikkit]

SAS Tom said:

In my head it shouldn’t be too disastrous due to the torque converter. Interested to see what the answer is though.

True, but if you have a TC which is worn it can accelerate the condition. My wife killed a Subaru one which was on 140k miles in fairly short order from doing this.

[cliffords]

My wife killed a Jeep this way. She is currently trying it with a Skoda SUV.
The Jeep box mechanically desintergrated. It was a write off.

My son and I watched her go off from our drive a couple of weeks ago. Changing direction from reverse in forward gear and chirping the tyres.

We have known each other for 43 years, I can't stop her doing it . So I don't try now .

[Panamax]

CraigyMc said:

If it's a regular torque converter, then it'll not cause damage. She's just shearing the hydraulic fluid in the torque converter a bit more than normal, but that's no different than starting the car moving up a hill or towing a load.

The clutches and bands are what engage the gears. The torque converter is just the somewhat flexible coupling that connects engine to the gearsets which are engage via the clutches and bands. And, as its name suggests, it transmits a lot of torque.

Putting an auto in reverse when the car's going forwards is almost exactly the same as doing it in a manual. I doubt you'd say in a manual, "it doesn't matter, the clutch can take up the difference just like moving off from stationary".

[csd19]

Decky_Q said:

If she does it quickly it should be fine, but the advise is to stop because you go through park and there is a locking pawl on the gearbox for park, if shes got the nack of doing it without letting it engage then fine (or the tip is already broken off many miles ago)

Nope. The gear pattern is P-R-N-D so from reverse to drive is just straight through neutral, no engagement of the parking pawl is done .

[dbdb]

My late father used to do this fairly regularly. It would make me wince even as a kid but he never had any transmission problems on any of his cars over several decades of doing it.

[CraigyMc]

Panamax said:

CraigyMc said:

If it's a regular torque converter, then it'll not cause damage. She's just shearing the hydraulic fluid in the torque converter a bit more than normal, but that's no different than starting the car moving up a hill or towing a load.

The clutches and bands are what engage the gears. The torque converter is just the somewhat flexible coupling that connects engine to the gearsets which are engage via the clutches and bands. And, as its name suggests, it transmits a lot of torque.

Putting an auto in reverse when the car's going forwards is almost exactly the same as doing it in a manual. I doubt you'd say in a manual, "it doesn't matter, the clutch can take up the difference just like moving off from stationary".

In a manual, the clutch is usually a couple of dry plates that rub together. Every time they slip, they wear.
In a torque converter auto the same thing is not true. It's fluid being sheared between impellers, and it can do it indefinitely without any wear at all because the shear fluid doesn't wear out.

[Matt_T]

csd19 said:

Decky_Q said:

If she does it quickly it should be fine, but the advise is to stop because you go through park and there is a locking pawl on the gearbox for park, if shes got the nack of doing it without letting it engage then fine (or the tip is already broken off many miles ago)

Nope. The gear pattern is P-R-N-D so from reverse to drive is just straight through neutral, no engagement of the parking pawl is done .

I've just checked and it's P-R-N-D, so it's not going through P each time, just going through N.

[Matt_T]

CraigyMc said:

Panamax said:

CraigyMc said:

If it's a regular torque converter, then it'll not cause damage. She's just shearing the hydraulic fluid in the torque converter a bit more than normal, but that's no different than starting the car moving up a hill or towing a load.

The clutches and bands are what engage the gears. The torque converter is just the somewhat flexible coupling that connects engine to the gearsets which are engage via the clutches and bands. And, as its name suggests, it transmits a lot of torque.

Putting an auto in reverse when the car's going forwards is almost exactly the same as doing it in a manual. I doubt you'd say in a manual, "it doesn't matter, the clutch can take up the difference just like moving off from stationary".

In a manual, the clutch is usually a couple of dry plates that rub together. Every time they slip, they wear.
In a torque converter auto the same thing is not true. It's fluid being sheared between impellers, and it can do it indefinitely without any wear at all because the shear fluid doesn't wear out.

Good summary CraigyMc.
So would I be correct that in VAG DSG (as with the Skoda above) this would wear out the clutch (I think that they always have a mechanical coupling?).
Also, a CVT (as with Subaru above) uses clutches to reverse the direction of the output shaft, so on these the clutch would wear out.
However, on my torque converter as there is no mechanic coupling (only fluid coupling) it's not going to do any damage.

[s94wht]

Matt_T said:

Good summary CraigyMc.
So would I be correct that in VAG DSG (as with the Skoda above) this would wear out the clutch (I think that they always have a mechanical coupling?).
Also, a CVT (as with Subaru above) uses clutches to reverse the direction of the output shaft, so on these the clutch would wear out.
However, on my torque converter as there is no mechanic coupling (only fluid coupling) it's not going to do any damage.

I will hold my hands up and say that I do kind of do this in my DSG. Not to a huge extent, but I'm probably slightly rolling forwards when I go into reverse. I don't think it's enough that anyone in the car would even notice. I figure that since the box is all electronic, it'll be smart enough to not engage reverse until it's actually stopped. I have often wondered what would happen if you were travelling at usual speeds and then tried to ram it into reverse, but for obvious reasons I'm not going to try that.

[CraigyMc]

Matt_T said:

CraigyMc said:

Panamax said:

CraigyMc said:

If it's a regular torque converter, then it'll not cause damage. She's just shearing the hydraulic fluid in the torque converter a bit more than normal, but that's no different than starting the car moving up a hill or towing a load.

The clutches and bands are what engage the gears. The torque converter is just the somewhat flexible coupling that connects engine to the gearsets which are engage via the clutches and bands. And, as its name suggests, it transmits a lot of torque.

Putting an auto in reverse when the car's going forwards is almost exactly the same as doing it in a manual. I doubt you'd say in a manual, "it doesn't matter, the clutch can take up the difference just like moving off from stationary".

In a manual, the clutch is usually a couple of dry plates that rub together. Every time they slip, they wear.
In a torque converter auto the same thing is not true. It's fluid being sheared between impellers, and it can do it indefinitely without any wear at all because the shear fluid doesn't wear out.

Good summary CraigyMc.
So would I be correct that in VAG DSG (as with the Skoda above) this would wear out the clutch (I think that they always have a mechanical coupling?).
Also, a CVT (as with Subaru above) uses clutches to reverse the direction of the output shaft, so on these the clutch would wear out.
However, on my torque converter as there is no mechanic coupling (only fluid coupling) it's not going to do any damage.

VW DSG is a marketing term for a load of what were initially borg-warner developed double-clutch gearboxes. These days it includes including wet and dry clutch plate types. Fundamentally though, DSG boxes don't have torque converters so do wear out their clutches -- in fact, it's two clutches in the same transmission system (the reason it shifts quickly is that it's just disengaging one clutch while engaging the other).

DSG/PDK is the same concept - two clutches, one transmission, with the gear not currently driving/engaged being preselected by some logic or other (usually if your foot's on the gas it's going to be the next gear up, and if you're braking, it'll be the next one down, but that's totally on the developer to decide). All have similar problems if the logic guesses "wrong" (you get exposed to how slow the actual gear selection mechanism is, which is usually like 10x slower than the part that bangs the clutches in/out.

[_Hoppers]

What happens when you engage reverse at 62 MPH?

[CraigyMc]

_Hoppers said:

What happens when you engage reverse at 62 MPH?

You go to 1955?

Oh, wait, that was 88mph.