N or EOC in an automatic Tacoma? - Fuel Economy, Hypermiling, EcoModding News and Forum

tacopower · 01-05-2013, 10:11 PM

I've heard conflicting things about coasting with an automatic transmission. Will doing either of these damage the engine or transmission? why exactly does this happen? I have a 2012 toyota tacoma 4x2 automatic.

2000neon · 01-05-2013, 10:20 PM

I can't imagine that coasting in Neutral will hurt it, but that depends on how it reacts going back from neutral to drive, if it clunks or makes any other indication that it's not happy I wouldn't do it too much. As far as coasting with the engine off, see if the truck can be "flat towed", which means being towed with all 4 wheels on the ground. If it can't, or it doesn't specifically say that you can, I would leave the engine on.

The reason is with the rear wheels turning, so is your driveshaft and transmission, if the oil pump for your trans runs with the torque converter, you NEED to have the engine running to pump fluid to keep everything lubricated, even while coasting.

tacopower · 01-05-2013, 10:42 PM

Thanks. I checked the manual and it says that it can not be flat towed, which I guess is equivalent to EOC.

So if the engine is idling in N it will still be pumping (enough?) fluid for the driveshaft/transmission?

2000neon · 01-05-2013, 11:17 PM

Since it says not to flat tow, I would NOT do any engine off coasting.

Yes, even in neutral the torque converter and oil pump will still pump enough fluid. I don't know the exact details of your truck, but in general in the vast majority of vehicles it is fine. The torque converter is attached to the flywheel of the engine, and spins with the motor, so even in neutral it will still pump enough fluid to keep the trans lubricated.

A little while back my old Neon (automatic trans) was having some problems and had to tow it a short distance home, but wasn't worth a tow truck, so we just flat towed it. It wasn't very far, and we were just towing at slow speeds, but what I did was put it in neutral and ran the motor to keep from hurting the transmission. It burned fuel that way but I figured it was worth it to save me any more for repairs.

mechman600 · 01-06-2013, 11:51 AM

EOC for short distances (<1/2 mile) won't hurt even if you are not supposed to flat tow your truck.

nemo · 01-06-2013, 01:39 PM

Quote:

Originally Posted by mechman600

EOC for short distances (<1/2 mile) won't hurt even if you are not supposed to flat tow your truck.

This assumes the transmission is in good condition and done at low speed. Better to follow towing recommendations.

mcrews · 01-06-2013, 07:11 PM

As a point of safty, I would NEVER 'engine OFF coast' w/ an automatic. With a standard I'm ambivolent.
The 'trick' is Does the rpm drop to idle in neutral coast? My Infinti drops to idle, so does my Kia sportage. I think my 97 Toyota Avalon did also (that was 7 yrs ago so I'm cant say for sure)
I drove a Ford Tauras for a week and it didnot drop to idle. so there was little or no gain in mpg.

Chisel86 · 01-14-2013, 02:31 PM

When you coast in gear (in a modern fuel injected car), it actually doesn't use any fuel at all, as the car is now pushing the engine and the computer knows this. Whereas when you coast in "N", when the engine slows to idle speed, it actually uses fuel to stay running.

This does not apply to cars with carburators and fuel pumps not controlled by an ECU.

mcrews · 01-14-2013, 02:38 PM

Quote:

Originally Posted by Chisel86

When you coast in gear (in a modern fuel injected car), it actually doesn't use any fuel at all, as the car is now pushing the engine and the computer knows this. Whereas when you coast in "N", when the engine slows to idle speed, it actually uses fuel to stay running.

This does not apply to cars with carburators and fuel pumps not controlled by an ECU.

So you said (if I understand) that when IN GEAR w/ENGINE ON, NO FUEL flows to the engine when coasting down.
And At NEUTRAL COASTING enough fuel flows to idle the engine.

Need some proof on that.

Because the spark would have to be turned off also. And I just cant see that happening.

That is technology that is VERY similar to "engine off" at lights like BMW is bragging about in their commercials on the 3 series

user removed · 01-14-2013, 02:46 PM

Automatic transmissions require fluid pressure to function properly Most run the primary pump off the back of the torque converter which required the engine to be running. I have seen them destroyed by towing, mostly Nissans in my experience. I would not even consider coasting with the engine turned off in your Toyota, unlesss you had specific information from the manufacturer that clearly stated they would cover any warranty issues even with engine off coasting.
Why chance a rejected warranty claim that they can prove with the information stored in your ecu.

regards
Mech