Coasting with an AT

[Jon M]

My Civic is (unfortunately) an automatic - first one I've owned.

Is it hard on an auto tranny to put it into neutral to coast for a bit then put it back in drive? And does it matter how fast you're going?

Obvisouly I don't want to "Try it and let us know!".

I don't know much about that type of stuff so any help is appreciated.

[digitaldissent]

I do it all the time with my Yaris, I shift from N to D at 60mph works great and have coasted down hill at 80+ for long distances. I do however leave the engine running to make sure the auto-tranny get lubed properly.

hope that helps

[Daox]

Well, there is going to be some additional wear. How much? Probably not a ton. When you do put it back into D make sure you rev match to minimize wear.

[Jon M]

Yeah, normally I'll do it coming up to a light or something so that I know I'll come to a complete stop, then put it in drive at the green light.

That brings up another question, what is the most efficient way to idle an auto?

Put in Park, Neutral, or Drive with foot on brake?


Thanks for the other info!

[digitaldissent]

in drive you are loading down the engine and in park you have to go back through reverse and neutral to get to drive.

On my car I just go up one spot to N when stopped or coasting then just one spot down for drive, makes it real easy and fast

[Jon M]

Originally Posted by digitaldissent

in drive you are loading down the engine and in park you have to go back through reverse and neutral to get to drive.

On my car I just go up one spot to N when stopped or coasting then just one spot down for drive, makes it real easy and fast

Pretty much what I figured. With an 11 year old tranny, I just want to be careful.

[RH77]

Originally Posted by Jon M

Pretty much what I figured. With an 11 year old tranny, I just want to be careful.

I have the same concerns, and a similar transmission ('98 Integra Auto). I usually just bump it up into Neutral to coast or short-idle, and back into D (rev-matched while in motion).

I see it this way. The 135,000 miles on the car are mostly "highway" miles. This means that city-like driving (extra shifts in any form) would wear more, but by how much? I've heard of this model of transmission lasting into the 200,000 range in fleet use (deliveries, etc.), which is the true test of extremes.

I can't guarantee that it won't give out tomorrow, but the added wear with a bit more maintenance can't hurt too much in its current state.

I read in another post that it's a recent purchase -- how many miles on it?

RH77

[Jon M]

Originally Posted by RH77

I read in another post that it's a recent purchase -- how many miles on it?

RH77

160,000

[elhigh]

I shift the Forester into and out of gear at speed all the time. Doesn't seem to hurt it any. Rev match is simple: observe what your engine is turning at a certain speed; when you coast down to that speed, jazz the gas to spin the engine up to about the right revs, and drop it into D. Tranny hooks up with minimal jolting.

Don't be at high throttle positions when you drop into gear or the tranny may see the low vacuum as a suggestion for a lower gear - VERY exciting, and not in a good way. I tend to buzz past my engine's set speed, then let it meander back to the correct revs and engage it while the engine is coasting down (sometimes under very light throttle, or else it settles back to idle too quickly) - guarantees highest gear on engagement.

Try it a few times at low speeds on a deserted road to get the feel for it.

[RH77]

Originally Posted by elhigh

Don't be at high throttle positions when you drop into gear or the tranny may see the low vacuum as a suggestion for a lower gear - VERY exciting, and not in a good way. I tend to buzz past my engine's set speed, then let it meander back to the correct revs and engage it while the engine is coasting down (sometimes under very light throttle, or else it settles back to idle too quickly) - guarantees highest gear on engagement.

Try it a few times at low speeds on a deserted road to get the feel for it.

Ah, the dreaded "Tranny-Bomb" -- although in partial form (full throttle N-to-D shifts at speed will grenade an automatic after a few times). It's safer to be under the RPM engagement point, in most cases, than over.

Something that hasn't been brought up. Engine-off coast (EOC).

(By all means, if you're considering it: practice, practice, practice -- without traffic or obstacles).

It hasn't been 100% confirmed that it reduces transmission life, but Honda transmissions generally aren't rated for towing with the drive wheels in motion.

I started EOC'ing about 30-40K miles ago (2 or so years). I also tightened the throttle cable for firmer shifts (less slippage), and should be 1/4 of the way through changing out to a near-full synthetic fluid. EOC increased my FE quite a bit. As the vehicle ages, I am backing-off of this procedure. Instead, I've replaced it with lower top speeds and downshifting for DFCO (who knows if that's wearing anything out -- probably). The shifter is a busy place these days.

I assume your car has that darned "Hill-Logic Control" to gear-hold up hills or down steep ones. EOC will confuse the daylights out of the TCU's calculations, and TC lockup may be significantly delayed (especially if EOC'd at high speeds).

Armed with that info, if you want to play it conservatively, neutral coast with a rev match (if you do it just right, over 35 MPH, it should be unnoticeable followed by a little shift with the TC engagement). Shutting off at lights/etc and back to drive shouldn't be that big of a deal.

RH77