Coasting with an Auto

[kickflipjr]

Today was the first time i tried drifting down a hill (engine not on). I just put into N, killed the engine, coasted down this one hill for about a mile, and then restarted when it was needed. I have heard that this can be bad for certain auto trannies. I have also heard that it isn't bad on saturns (i don't plan on doing this too often because it is hard on the starter).

[MetroMPG]

yay - another convert!

a mile is a long coast (by local standards). one of my longest around here is maybe half a mile - IF there are no trains coming AND the light after that is green.

[Compaq888]

this is the reason I stopped coasting with engine off. It can kill the tranny easy, and starter. I hate auto.

[kickflipjr]

I used to do it with my old car (5 speed). It just seems dumb with an auto.

Yeah, that hill is nice, long, and not too steep. I have bee coasting it in nutral for years.

[Compaq888]

I don't think coasting with engine on in neutral will damage anything, there will be less resistence but the problem is you can't put it into the gear you want

[rh77]

So, today I tried the coast/engine off in a few places. With the driving I do, I ended up doing it approx. 15 times. If I don't let the transmission kick-down to first gear before a light, then the N-to-D shift is jolting once things get going again. I coasted down a hill, engine off for half a mile and started back up. I've been using the N-idle feature at long lights if I know it isn't planned to change within 20 seconds. Otherwise, I've been trying the shut-down. I have to pay close attention to the traffic pattern, or else I get stuck dead in the water until things get back up and running, and irritated people behind me. Cutting the power deactivates the turn signal for a second or two -- I may look into the engine cut if I get decent evidence that I'm not trashing the transmission. So yes, MetroMPG, I have seen the light, and I'm now converted.

RH77

[Compaq888]

rh77,

so let me get this straight, you coast in N then put it into D? Wouldn't that N bomb the transmission???

Can you make it work like this... See a red light ahead, flip to N, shut down engine. Stop at red light, green hits restart engine, put in D and keep going??

Can you put the shifter from D to N without causing any damage?

[Compaq888]

Here is what I did this morning. When I drive and see a yellow or red light I put in N and let it coast to the light. If I know it's going to be a long light when I put it into N I shut the car down too. When I get to the light I stay there till it turns green and restart the car and put back in D. If the light will be soon I just coast up to the light in N and leave it in N and wait for the green. When the green hits I put in D and drive off.

[rh77]

Originally Posted by Compaq888

rh77,

so let me get this straight, you coast in N then put it into D? Wouldn't that N bomb the transmission???

Can you make it work like this... See a red light ahead, flip to N, shut down engine. Stop at red light, green hits restart engine, put in D and keep going??

Can you put the shifter from D to N without causing any damage?

As far as I know, you can't damage the transmission from shifting to D-N or N-D without throttle input. N-bombing the tranny is putting the car in neutral when you're moving, say 65 mph, then in N go full throttle and shift into D. Since it's not a standing start bomb, it probably wouldn't tear things-up immediately, but a few times and it's shot.

RH77

[rh77]

So, I took a VAC up to Calgary and their National Parks in the Rockies over a long weekend. Down a long hill on the Trans-Canada Highway 1, I put the rental Chrysler 300 into N and shut off the car. It coasted at the speed limit down the mountain. When it was time to start it back up, it wouldn't! Dead in the water, we coasted to a conveniently located turn-out on the side of the road. I had to turn the key to the complete OFF position and then start the car! If I did that moving, it would've locked the steering, potentially screwing us even further. I have some Canadian car stories to tell in a separate thread, but MetroMPG, I saw my first Pontiac Firefly!

RH77

[philmcneal]

Originally Posted by rh77

So, I took a VAC up to Calgary and their National Parks in the Rockies over a long weekend. Down a long hill on the Trans-Canada Highway 1, I put the rental Chrysler 300 into N and shut off the car. It coasted at the speed limit down the mountain. When it was time to start it back up, it wouldn't! Dead in the water, we coasted to a conveniently located turn-out on the side of the road. I had to turn the key to the complete OFF position and then start the car! If I did that moving, it would've locked the steering, potentially screwing us even further. I have some Canadian car stories to tell in a separate thread, but MetroMPG, I saw my first Pontiac Firefly!

RH77

Hahaha Chrysler is a brand I will nevrer call my own. But glad your safe so TEST N coast with engine off in a clear area folks! Do it in the wrong place and boy you'll never want to drive EVER again.

[DaX]

Originally Posted by rh77

As far as I know, you can't damage the transmission from shifting to D-N or N-D without throttle input. N-bombing the tranny is putting the car in neutral when you're moving, say 65 mph, then in N go full throttle and shift into D. Since it's not a standing start bomb, it probably wouldn't tear things-up immediately, but a few times and it's shot.

RH77

Haha, now I'm thinking of N-bombing my auto tranny right before I do the 5-speed conversion, just for the hell of it and to see how many times it takes to kill it. Just talking about N-bombs makes me LoL.

[Matt Timion]

Originally Posted by DaX

Haha, now I'm thinking of N-bombing my auto tranny right before I do the 5-speed conversion, just for the hell of it and to see how many times it takes to kill it. Just talking about N-bombs makes me LoL.

LOL... "N-Bombs" almost sound like a cuss word.

[rh77]

So, I've tried that a few times in a Rental just to see what would happen (never from a standing start), and it just kind of slips into whatever gear is appropriate and off you go! It's kinda like slipping the clutch in a manual. Evidently, it tears it up. (Didn't know that at the time -- I feel guilty about ripping up Rentals sometimes, because some poor sucker is going to buy it off of a used lot in a year or two. The roughest I've been is with that Chevy Trailblazer on the Rally stages -- particularly the last one where I beat the last 6 car's times.

So, if someone refers to the car as the "N-bomb", I'd be cautious ;-)

RH77

[rh77]

Originally Posted by Matt Timion

LOL... "N-Bombs" almost sound like a cuss word.

OMG, Bob dropped the N-bomb in front of the boss the other day. I thought he'd get fired on the spot!

RH77

[Compaq888]

Originally Posted by rh77

I feel guilty about ripping up Rentals sometimes, because some poor sucker is going to buy it off of a used lot in a year or two.

RH77

I hate you!!!!!!!!!!!!!!!
Me=owner of a previously rented car.

[rh77]

Originally Posted by Compaq888

I hate you!!!!!!!!!!!!!!!
Me=owner of a previously rented car.

Great now you hate me *tear*. What about all the good times we had together here on Gassavers: the O/D discussion, your quarter-mile times. I've ruined it.

OK, now go back and re-read my post. I rent, on the average, 1-2 cars per week. 99% of the time I wouldn't ever do anything that would compromise the longevity of the vehicle. If you polled most people our age out there, they would tear the living **** out of rental cars: throwing it in reverse on the highway, jumping it over hills, driving at redline all day. I'm one of the good guys out there that rents cars. I may have compromised 1 or 2 cars out of almost 500 I've rented in my life. 1 was the Rally trailblazer -- the paint was scuffed. The other was the accidental N-Bomb before I knew the consequences. Go ahead and hate me, but be warned -- there are much worse people out there in the rental world.

My parents bought a used Jeep Grand Cherokee for their Farm, which was a rental. The transmission went out at 160,000 miles and they had miscellaneous problems -- they got a good deal on it, but it was a rental. Anymore, I picture someone like my folks buying the vehicle. Does that make you feel any better ????????

RH77

[Compaq888]

Originally Posted by rh77

Great now you hate me *tear*. What about all the good times we had together here on Gassavers: the O/D discussion, your quarter-mile times. I've ruined it.

OK, now go back and re-read my post. I rent, on the average, 1-2 cars per week. 99% of the time I wouldn't ever do anything that would compromise the longevity of the vehicle. If you polled most people our age out there, they would tear the living **** out of rental cars: throwing it in reverse on the highway, jumping it over hills, driving at redline all day. I'm one of the good guys out there that rents cars. I may have compromised 1 or 2 cars out of almost 500 I've rented in my life. 1 was the Rally trailblazer -- the paint was scuffed. The other was the accidental N-Bomb before I knew the consequences. Go ahead and hate me, but be warned -- there are much worse people out there in the rental world.

My parents bought a used Jeep Grand Cherokee for their Farm, which was a rental. The transmission went out at 160,000 miles and they had miscellaneous problems -- they got a good deal on it, but it was a rental. Anymore, I picture someone like my folks buying the vehicle. Does that make you feel any better ????????

RH77

It was a joke, we bought our car from a nissan dealer that bought it at an auction from a rental place. The transmission shifts fine. My cousin messed it up, I fixed it by resetting both the ecu and the transmission module and taking out the extra liquid out of the tranny.

Now my moms car is messed up, I feel sorry whoever buys that.
Engine broke down twice, ecu went crappy and had to be reproggramed, sometimes looses power on the freeway, and other little stuff. Our lease will be over in Nov. this year.

Sorry for the confusion, I don't hate you.

[rh77]

I know -- I'm just playing along. But at the same time, I don't want people to think I'm going around tearing the crap out of rental cars. I go back to the same places, so I might end up with the same car, and I don't want to be stranded. Also, to encourage people not to tear-up rentals, because it's not the rental agency that's going to get screwed, it's someone who buys a "well-maintained, late-model" vehicle. I live about 5 miles from a huge car auction facility. I see hundreds of car model-types that I've rented. Many dealers from all over buy them and sell them as "One-Owner" cars. Who knows what people have done to them, that can't be found by a good mechanic. But really, that goes for any used car anymore. Buyer beware.

RH77

[DaX]

I can see it now...revving the engine to 6500 RPM's...burning oil smoke blowing out of the exhaust pipe [the car burns oil horribly at high rpm's]...slamming it into drive...the squeal of tires and the smell of burnt clutch packs. I just may have to indulge myself.

[Compaq888]

be sure to post the results of how many N bombs it takes to kill the tranny.

[DaX]

Originally Posted by Compaq888

be sure to post the results of how many N bombs it takes to kill the tranny.

"How many licks does it take to get to the center of an auto tranny?"

I've N-bombed twice before from what I believe to be about 3500 RPM's (didn't have a tach back then). If I decide to do it I'll be bouncing off the rev limiter. Go all out.

[philmcneal]

so with an auto tranny coasting with engine off in N ... say your going 10-15 mph and you decided to put it back into D. Would the engine magically start up again (roughly hense the name bombing) that would be cool! Or you have to key on?

I noticed some Volkswagaons have a DSG (its a manual transmission controlled by the "best manual driver in the world" i wonder if the computer is smart enough to bump start the engine smoothly...

too good to be true stop dreaming~~

[Compaq888]

The vehicle has to be in N or P in order to restart.

[zpiloto]

DaX:

I've N-bombed twice before from what I believe to be about 3500 RPM's (didn't have a tach back then). If I decide to do it I'll be bouncing off the rev limiter. Go all out

It would be cool if you could record the audio and post it so we could hear the full effect.

[rh77]

I did it with a Pontiac Grand Am a few years ago. Basically you're traveling along at any speed and shift to N. Then Rev it up bumping off of the rev limiter -- that's the loudest sound. Then shift to D. You'd think it was a big production, but it isn't, really. Then oddly enough, the transmission makes little noise. The engine just bogs down while the tranny catches and figures out the right gear like if you were to rev up a car with a clutch and let it out slowly. Then the car acts normal with a downshift for power acceleration unless it's been fried.

RH77

[zpiloto]

Can some one help me with why it destroys your auto transmission if you coast in neutral with the engine off. I've never seen the inside of a transmission and looking around on-line it doesn't really address the issue it always get side tracked into legality, brakes and PS. The torque converter is a fluid coupling and with it in neutral the axel is still hooked up to the transaxel so the gears are still spinning around no harm there. But when you shut the engine off it shut down the pump. Now where is the pump pumping fluid to? Even when the pump is off the gears will still have fluid from when it was on and there is no load. So does a coast of 30-60 second at speeds under 50 MPH cause that quick of a heat build up? and what parts are geting damaged? I can see where if you flat towed it cold for miles it would cook everything.

[n0rt0npr0]

With no fluid *pressure* the auto transmission disengages completely. There is absolutely no way for this engine off coasting in gear or out to destroy a tranny.

However IF you have an electronic transmission, IT WILL most likely confuse the **** out of the tranny. Thats why Compaq888 was having a hard time with his in the first place. It's all because of the way they designed the "fuzzy logic" ....either the engineers factor in that the driver won't use engine off coasting (ie, compaq888) or they will factor in engine off coasting (ie, 2001 olds intrigue)

[psyshack]

I coast our 05 Accord 5AT all the time. ICE off,, ICE on. restart engine and dump it in drive.

[Compaq888]

Originally Posted by psyshack

I coast our 05 Accord 5AT all the time. ICE off,, ICE on. restart engine and dump it in drive.

your tranny must be designed differently than mine. I'm still getting good mpg with coasting in D. Whenever you let your foot off the gas the tranny goes automatically into neutral, the reason the car slows down so much is it's connected to the engine. When you put the lever in N you actually disengage the tranny from the engine and you get a longer coast because your engine is not slowing down the tranny.

It's actually pointless to just stick it in N and coast because the engine still injects fuel. If you're going to stick it to N you better shut off the engine to save fuel. On my car if it's in D and I coast the fuel injection shuts off till like 1000-1100rpm then comes on to prevent the engine from stalling.

You can find out a lot by reading a FSM for your car. If you have one look in the Electronic control section.