Coasting???? - Toyota Nation Forum : Toyota Car and Truck Forums

10thanntransam · 09-09-2008, 06:24 PM

I have a 2008 V6 Automatic TRD Sport. I drive 100 miles a day to work, and at night on my way home, I drive down alot of hills on the Turnpike. I place the transmission in neutral, and coast about 4 miles a night. That is 20 miles a week, which helps out the mpg, and I maintain 70-75 mph while doing this. I read a blog a few weeks ago that said that could be harmful to a transmission. Anybody have any comments about this???

NOhara24 · 09-09-2008, 06:29 PM

Youre not supposed to be actively shifting an automatic. Theyre just not built for it. I could see a definite problem if you were shifting from "L" to "D" at every stoplight, but im unsure as to what youre doing could be harmful. Just let off the gas when you coast, saves MPG, and your brakes.

the.phantom · 09-09-2008, 07:33 PM

you ever notice that you see a two truck, they tow a auto so the
drive wheels are off the ground? i asked and they said it is hard on the tranny as parts are turning but lube is minimum

just my 2 cents worth

worthywads · 09-09-2008, 07:54 PM

Your transmission will be fine so long as the engine is still running. Damage will result only if you turn your engine off while coasting. With the engine running fluid is still being circulated, no engine no lube.

If you are coasting at 70-75 in neutral and also braking you are probably better off to keep it in gear and let the engine brake, you get full fuel cutoff during engine braking. Pop back into gear instead of braking as needed, save fuel and your brake pads.

steve-m · 09-09-2008, 09:22 PM

Most automatic drivers don't realize how much they are using their brakes under NORMAL conditions, let alone flying down a steep hill with no resistance.
I'd keep it in gear. It'll be easier on the brakes, and may prevent a panic situation if your brakes overheat.

buzz5 · 09-09-2008, 09:30 PM

Quote:

Originally Posted by 10thanntransam

I have a 2008 V6 Automatic TRD Sport. I drive 100 miles a day to work, and at night on my way home, I drive down alot of hills on the Turnpike. I place the transmission in neutral, and coast about 4 miles a night. That is 20 miles a week, which helps out the mpg, and I maintain 70-75 mph while doing this. I read a blog a few weeks ago that said that could be harmful to a transmission. Anybody have any comments about this???

So;what you are saying is that you risk very exspensive damage to different parts of your new truck to save about a gallon of gas a week?That's not much help,as you call it,to risk the damage,not to mention possible safety issues like if you needed to manuever quickly for some reason.It cracks me up to read about people who but these 4x4 trucks and then start wanting to make them gas misers!These are performance minded mid-size trucks!You want a gas saver-- buy a Civic.

Splicer · 09-09-2008, 10:47 PM

Not sure how accurate your mpg calculations are; you may actually be using more fuel when coasting.

When coasting in neutral, your engine is using enough fuel to keep it running at idle speed. Granted it's not much, but it is using fuel.

If you are coasting (foot off the throttle) in gear, no fuel is needed to keep the engine turning over. There's no trip computer on my Tacoma, but my Jeep had one -- and it indicated 99 mpg, as high as it could register, when coasting downhill in gear.

Be interesting to hear from guys who have installed a Scanguage in their Tacoma...

bassman444 · 09-09-2008, 11:50 PM

Quote:

Originally Posted by Splicer

Be interesting to hear from guys who have installed a Scanguage in their Tacoma...

That would be me, and the data says:

Do not put your auto in neutral. I don't know about engine damage, but on the mileage side shifting into neutral will hurt your mileage.

This is because the fuel shuts off and the engine turns over on inertia when you are coasting downhill - while doing this the scanguage registers 9999mpg and 0.0gph. Neutral requires about .37gph all the time whether the truck is coasting or not. You should also avoid shifting into neutral at stoplights/drive thrus/etc because the fuel burn is only about .33gph in drive with no movement.

So by shifting into neutral going downhill, you are possibly putting unneeded wear on your tranny and you are reducing your mileage.

rdsaustintx · 09-10-2008, 12:10 AM

So yer slapping that puppy from neutral into drive at 70mph??

***08TRDOFFROAD*** · 09-10-2008, 08:14 AM

Quote:

Youre not supposed to be actively shifting an automatic. Theyre just not built for it. I could see a definite problem if you were shifting from "L" to "D" at every stoplight, but im unsure as to what youre doing could be harmful. Just let off the gas when you coast, saves MPG, and your brakes.

I would like to see some written proof that shows there is damage done to the transmission by shifting on the fly. I don't think the transmission would allow you to shift if it could cause damage. I could understand if the OP was reving in neutral and then slapping it into drive and spinning the tires. That will cause damage. But how is shifting from D->4->3->2 and then back up going to damage the transmission?

I drive a fairly steep canyon(Parley's, for those that are familiar with the area) where I live, I use the transmission to down shift to keep my speed under control so that I do not have to ride the brakes the whole way down...I have not had any ill effects.

But apparently it is a good thing I bought the 100k extended warranty....

worthywads · 09-10-2008, 08:55 AM

Here's a link to a discussion on the pros/cons of coasting with an automatic. It pretty much dispels the idea that shifting from N to D and back at 70 is harmful.

http://www.cleanmpg.com/forums/showt...mission+damage

Quote:

Originally Posted by MaxxMPG

There is a big difference between N to D while coasting and while the engine is runnning at 7000rpm. What most people miss in these discussions is that transmissions have overrunning clutches - either sprag or roller type - to allow the output shaft to freewheel. These clutches serve two major purposes.
First, they allow smooth shifting of gears by absorbing the sudden change on output shaft speed as the shift from a 2.5:1 gear to a 1.5:1 gear occurs. There would be an awful 'bang' if this happened without an overrunning clutch that allowed the clutch drum to freewheel. When you shift to Low and you feel the engine braking, what you are feeling is a band or clutch applying to prevent that freewheeling.
Second, they allow the output shaft to spin faster than it would spin if powered by the engine while in Drive. Unless Low range is selected, and a band/clutch applied to prevent the overrunning, the car will freewheel.
Anyone who has ever ridden a multi-speed bicycle has had first hand experience with with a sprag clutch. There's one in the hub of the wheel or pedal crank to allow you to stop pedaling while the bicycle keeps moving. While bicycles don't have "Neutral", you can stop pedaling at any time, and that is analagous to N in that power is not being transmitted. If you start pedaling again, power will be transferred to the wheel as soon as you pedal fast enough to "catch up" to the road speed for the given "gear". Transmissions have a fluid coupling which makes this action even smoother.
So on the highway, shifting from N to D, the transmission will apply the forward clutch and the direct clutch. Transmission designs vary widely, but most will apply two clutches to provide direct drive. At a lower road speed, 2nd or even 1st may be selected. Either way, if the wheels and output shaft are spinning faster than they need to, the sprag clutch will allow this difference in speed.
So you don't need to worry about shifting N to D to N and so on. It's not the same as a 7 grand "neutral drop". If there were any chance of abnormal wear (or worse), the manual would clearly state that this shifting action would damage the transmission. Or, the transmission controller would be programmed to refuse to select a gear when moving back to D.

lrak · 09-10-2008, 09:57 AM

Quote:

Originally Posted by NOhara24

Youre not supposed to be actively shifting an automatic. Theyre just not built for it.

I completely and totally disagree. Myths like this are one of the reasons manual drivers think autos suck. I've always shifted my manuals and never had a problem with it. The computer does the same thing after you downshift with the stick as it would do if you encountered a hill and stepped on the gas. sheesh.

***Bakemono*** · 09-10-2008, 05:26 PM

I dont see how shifting into neutral while going downhill is going to save any signifigant amount of gas.
I also disagree with the notion that you will damage an automatic by shifting it manually. If that were the case, there would be no such thing as automatics that have a manual mode (autostick).
As long as you have your foot off of the gas when shifting from neutral to drive, I dont think there is enough load being put on the driveline to cause damage.

***lotust*** · 09-10-2008, 05:37 PM

NOhara24 · 09-10-2008, 07:19 PM

Quote:

Originally Posted by lrak

I completely and totally disagree. Myths like this are one of the reasons manual drivers think autos suck. I've always shifted my manuals and never had a problem with it. The computer does the same thing after you downshift with the stick as it would do if you encountered a hill and stepped on the gas. sheesh.

Before you "completely and totally disagree" with my post, do yourself a favor and read the whole thing and understand what im referring to. Going from L to D and back everytime you stop WILL be harmful, effects may not be immidiate, if you still "completely and totally disagree" try it, and get back to me in 100k. Ill still be here.