Shifting into neutral kills tranny! What?

so shifting into nuetral to coast or maintain speed down a long hill is or isn't bad for it?

 

Not true, and that is why owners manuals say put the trans in neutral if it is overheating, it continues to pump, including through the cooler.

Yes there is an optimum range, and the Tacoma has a thermostatic control, that regulates fluid to the cooler, on the Tow package equipped vehicles only. It's in the FSM.

Not to be rude, but the last part is completly wrong. Flow does not stop, the torque converter does not interface with the planetaries, and planetary gears never decouple. And all the above has nothing to do with heat generation.
Sorry, but ASE is right.

 

It may astound you more to hear the DTC threshold limit is actually 9kms, not miles.

 

so, dumb question here, but if neutral is bad for the tranny, why is it even an option?? isnt the idea of neutral to remove the gears from the engine and allow it to spin naturally without any resistance??

 

FSM:

2. NORMAL MODE AND CHECK MODE​

(a) The diagnosis system operates in "normal mode"
during normal vehicle use. In normal mode, "2 trip
detection logic" is used to ensure accurate detection
of malfunctions. "Check mode" is also available to
technicians as an option. In check mode, "1 trip
detection logic" is used for simulating malfunction
symptoms and increasing the system's ability to
detect malfunctions, including intermittent
malfunctions.​

3. 2 TRIP DETECTION LOGIC​

(a) When a malfunction is first detected, the
malfunction is temporarily stored in the ECM
memory (1st trip). If the ignition switch is turned
OFF and then ON again, and the same malfunction
is detected again, the MIL will illuminate.​

4. FREEZE FRAME DATA​

(a) Freeze frame data records the engine conditions
(fuel system, calculated load, engine coolant
temperature, fuel trim, engine speed, vehicle speed,
etc.) when a malfunction is detected. When
troubleshooting, freeze frame data can help
determine if the vehicle was running or stopped, if
the engine was warmed up or not, if the air-fuel ratio
was Lean or Rich, and other data from the time the
malfunction occurred.
(b) The ECM records engine conditions in the form of
freeze frame data every 0.5 seconds. Using the
intelligent tester, five separate sets of freeze frame
data, including the data values at the time when the
DTC was set, can be checked.
• 3 data sets before the DTC was set
• 1 data set when the DTC was set
• 1 data set after the DTC was set
These data sets can be used to simulate the
condition of the vehicle around the time the
occurrence of the malfunction. The data may assist
in identifying of the cause of the malfunction, and in​

judging whether it was temporary or not.

 

i use it when im sitting for a while but not parked-- ie stopped to use the phone in a parking lot, long red light-- i figure its better than holding the brake, which is keeping the drive wheel from spinning, which seems like it could cause some wearing issues-- kind of like holding a fan blade when its turned on (idk best analogy i could think of)

 

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eh? you don't rev your engine you just put it in neutral. Also there is a benefit. You save gas. I know because I get about 3 to 4 more mpg if I hyper mile and use nuetral alot but I don't want to do it if it's bad for the tranny obviously. When coasting in drive with an automatic you engine break and thus lose speed which causes you to have to accelerate again and hold up other drivers. In neutral down long hills you can maintain speed using very little gas. Also you coast to lights farther and faster than in drive.

 

It's been posted many times, when the truck is coasting in gear, it uses ZERO fuel as the truck is equipped with a fuel cutoff. When you put it in neutral, the engine is fed enough fuel to keep it idleing. It's not worth buggering up the trans, to get worse mileage.

 

Yes. What you wrote makes sense. There is less friction generated by the transmission when your rolling down the road in neutral so it would make perfect sense that you would save gas and your MPG's would go up.

I am not a mechanic, but I can tell you that our automatic transmissions are precision instruments that are controlled by a computer. I don't think there is any real harm in occasionally hyper-mileing but I would not do it all the time.

Here is what the FSM states about our automatic transmissions:

 

It's been stated many times previously that the earth was flat too. Just because something is stated many times doesn't mean it's true. You are smoking crack if you think you get better milage in drive than in neutral sorry. I realise the injectors cut off fuel coasting in drive but the point is when you coast in drive you slow down quickly (engine breaking). So you have to accelerate again which burns alot of gas. I.e you can't go down a very long hill like the 15 coming back from vegas in drive you will slow down to an unsafe speed not so in neutral. In neutral with inertia and gravity you can damn near maintain 65.

putting in in neutral uses less gas. Just look on a scanguage.

 

The part I boldfaced, is not what We are disagreeing about. What we are in disagreement about is what is done with the fluid when the shifter is moved to "N". I am asserting that shifting to "N" simply dumps all fluid flow out of the pump, back to the transmission pan. If you are in neutral, then the vehicle should be stopped, and likewise the need to cool, pressurize, and lubricate anything would not be needed. Therefore from an engineering standpoint, the simple solution is to simply set up neutral to purge all fluid back to the pan. This is verified by the fact that the car will quit trying to creep forward, and all fluid flow through the transmission oil cooler stops. What I have seen in cutaways of an automatic transmission seems to me at least, to verify this.

 

I have a scangauge, netral coasts around 1.3 liters per hour, while coasting, in ger drops to 0 LPH. As in nothing. (Which tells me you don't own a Scangauge) Most of time, coasting is leading up to stopping, the fuel cuttoff helps re-capture some of the energy used to accelerate. Yes there are times when neutral will use less fuel, but in everyday driving, especially stop and go, it's not even close. Perhaps we are discussing 2 different things. I was mostly referring to normal driving, not coasting down a long grade. There is always an exception that proves the rule, and popping the trans in and out of gear while moving is a bad idea. Did you read the OP?
This is not a hyper miling forum. If you want to re-orginize you life to save gas, that's your business, buit's bad advice to say neutral saves gas. As a rule, for most people,it does not.

 

Every automatic transmission I've owned, feels like it "disconnects" from the drivetrain when coasting. I know it's not, but from my experience, there is far less engine braking with an automatic than a manual. I had a Chevy Impala a couple of years ago, that had an instant mileage computer on it. Taking my foot off of the gas in gear would yield incredibly long periods of 99mpg numbers. If I were to take it out of gear, the engine going to idle would drop those numbers into the 70's. I could post some wicked high mileage numbers in that car - well into econobox range.

 

No it does not, it merely disengages the lockup, and whatever ratio the transmission has selected at that point in time.

Not true, flow to the cooler continues. That is why most owners manual say to put it in neutral, and sometimes rev the engine to cool down the trans.

You musta missed my reply
http://www.tacomaworld.com/forum/2n...-neutral-kills-tranny-what-4.html#post1640293

 

If you pull the overflow plug on the ATF pan without the engine running you will get about a liter of fluid drain from the pan. This is normal as Toyota specifies that the fluid level be verified with the engine running in either park or neutral while the fluid is circulating within the AT.

With the proper amount of ATF in the pan:

- Remove plug with engine not running = ATF will drain from the overflow.

- Remove plug with engine running in P or N = NO ATF will drain from the overflow.

If placing the AT in neutral dumped all the fluid back into the pan, I would think that the ATF would drain from the overflow such as it would when the engine isn't running (since all the ATF is now back in the pan resulting in the level being higher than the overflow plug).

My $0.02

 

OK.. most Manufacturers of modern automatic transmissions redirect fluid flow away from the "cooler" during times when heat transfer to the fluid is low or the trans itself isn't yet up to 'temperature' (initial start-up, cold outside temps, neutral, park, etc..), in order to maintain a steady/average operating temperature range. This can be accomplished in an assortment of way, via thermostatic valves, feedback from PCM operated valves, etc....

As this info would be "technical" & manufacturer specific, it most likely wouldn't be included in articles discussing general transmission operation..

Again tho, please read the articles that I 'linked' to in a previous post, they should help you understand the basics, then what I'm trying to explain will make perfect (& common) sense..

 

Yes you are talking about something different and no it's not an exception. You don't have to reorganize your life to get an extra 3-4 mpg in our vehicles. Neutral is better than drive for coasting any sort of distance. Unless you are just approaching a traffic light, or an exit ramp that is a relatively short distance. In that circumstance I coast in drive.

Coasting in drive down a medium or long incline (15 back from vegas I frequently go out there to visit a friend.) Neutral wins hands down. In drive the vehicle slows down due to the engine breaking. You impede other traffic and eventually almost come to a stop. So you have to accelerate (read take a hit on mpg) I've tried both and it's better mpg in neutral on scangauge. Maybe you don't own one?

I guess you mean to "begin with" your assumptions are incorrect. A more fuel efficient car is unfortunately not an option for me currently. I would own a hybrid otherwise. I require a truck for hauling light to medium loads and I have a fondness of saving money. I definitely have the right vehicle! Furthermore I enjoy the gamelike challenge (when I'm in the mood) of getting better milage. Blasphemy. How dare you accuse a tacoma owner of not having "the right vehicle"!


All of this aside, I'm looking for someone to clearly demonstrate that using neutral is detrimental to the transmission, besides speculation. If so I will not continue to do so.

 

This has not been my experience from replacing Mitsubishi auto trannies in two different Hyundai's, and installing tranny temp gauges in one of those vehciles, as well as installing one in a Nissan Hardbody truck.

 

I did read them. I think I have read them before, as I have been facinated by the operating concept of automatics. How the planetary gearsets transmit power still makes me scratch my head.

 

The Toyota 'adaptive' automatic trans is one of the most technologically advanced transmissions of the 'original design' type autos..
However, there are auto transmissions out now in high end vehicles that put it to shame, newer concepts & methods of operation.
I wouldn't study the planetary gearset model too much, as it probably won't be around much longer.. Too many better & more efficient technologies are out already...

If you spend $100,000plus on a vehicle, you'll get the newest/best...

Finally.. I do not recommend putting the vehicle in neutral to 'coast', as these vehicles have 'adaptive transmissions' that will 'learn' incorrect information from this behavior, which defeats the purpose & benefit of being 'adaptive'..

However, no mechanical damage will occur...