Curious why "high" RPMs when coasting in neutral?

[TrippMe]

I was driving home from Mammoth Lakes heading downhill toward Bishop and I'm doing ~80MPH and I put it in neutral to have the engine RPMs still at ~2500.

Am I actually not in neurtral?

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[RichardCranium]

First off, I would not recommend doing this because the transmissions are not rated to roll at highway speeds in neutral. Only hybrids have dingy mode.
As for the RPMs of the engine, I believe that even in neutral, the fluid dynamics of the transmission will cause the gears to spin, even while in neutral. That torque is transferred to the engine through the torque converter and will cause the engine to spin up when at idle. It is that back pressure that is harmful to the the transmission. Neutral is designed to not give power to the rear wheels, but the spinning of the transmission from the back wheels causes the harmful back pressure.

 

[TrippMe]

Appreciate the response!

Wouldn't towing cause the same thing?

Transmission and Engine are not connected fluids wise (at least not when I last knew) so your explanation doesn't make sense to me.

Am I missing something?

 

[Thundercougarfalconbird]

I'm not sure if this is the situation, but I know some tunes will increase RPMs to match speed at higher speeds so you don't slam the transmission and damage it putting it back into D. Ford may have programmed that in here for that purpose.

May I ask why you'd switch to neutral in this situation?

 

[RR - All the way]

After turning a corner, I can "coast" a little over a mile and make it into my carport. If I go to neutral at over 30mph even though I am at about 12 to 1300 rpms, it will jump up to around 2000 rpms for a couple of seconds. Applying brakes does not bring it down. At about 25 mph or less it just goes to about 800 rpms. Mode is Eco

 

[TrippMe]

I don't have a tune installed.

I was just coasting down the very long hill to get some free milage.

No particular reason.

 

[Thundercougarfalconbird]

I don't have a tune installed.

I was just coasting down the very long hill to get some free milage.

No particular reason.

Sorry, meant tunes in other cars do it and might be what Ford programs in by default now to protect the transmission. I did some further reading on this topic tonight and apparently it's common now in modern vehicles to ensure a smooth transition back into D at the proper gear.

I asked why as you may be costing yourself mileage in this case. Fuel is cutoff when coasting in D as the engine is turned by the transmission through momentum. When you put it in neutral, the truck has to use fuel to get to run at idle speed (or apparently even higher in this case), so you're actually using more fuel, adding potential wear to the transmission, and potentially using more brakes (since no engine braking) over time.

 

[RichardCranium]

Appreciate the response!

Wouldn't towing cause the same thing?

Transmission and Engine are not connected fluids wise (at least not when I last knew) so your explanation doesn't make sense to me.

Am I missing something?

Fluid dynamics is the way the movement of fluids affect things. Torque converters work by using a turbine (fancy fan) to push your transmission fluid over another turbine. The turbines are slightly different in order to reduce rpm’s in a calculate able amount. At low speeds, the brakes can overcome the motion of the fluid and hold the truck in place, allowing the engine to spin but the transmission stays in place.
In neutral while moving, the motion of the fluid causes the gears to spin in a similar manor. This motion is transferred to the torque converter and back to the engine.
It is my understanding that the pressure created on the wheel side can increase higher than the pressure created by the pump on the engine side, causing fluid to press against the check valves and possibly damage them. It is not as likely to happen at low speeds, but at high speeds can lead to damage.

 

[Whatcolortochoose]

As others have said on these trucks and a lot newer vehicles. At best coasting in neutral will use more gas than coasting in drive and at worst damage the engine or trans. Either way its not good to do this.

 

[FamousAmos]

I'm not sure if this is the situation, but I know some tunes will increase RPMs to match speed at higher speeds so you don't slam the transmission and damage it putting it back into D. Ford may have programmed that in here for that purpose.

May I ask why you'd switch to neutral in this situation?

Good question. Why? It seems to me that shifting into neutral at 80 mph, then shifting back into gear is BEGGING FOR SOMETHING TO BLOW UP. "Nine things can happen and eight of them are bad." Be sure that when you finally put your Maverick up for sale that you tell the prospective buyer that you liked to shift from Drive to Neutral to Drive at 80 mph. I'm sure he'll get a kick out of it.

Damn, my sarcasm finally kicked in, and I expect to be kicked off this forum. I was on here for almost a year, which breaks my record. Woe is I.

 

[Oscarcat]

I was driving home from Mammoth Lakes heading downhill toward Bishop and I'm doing ~80MPH and I put it in neutral to have the engine RPMs still at ~2500.

Am I actually not in neurtral?

Having driven that stretch of beautiful 395 in the Eastern Sierras for over 30 years, [but not yet in my Mav] I have seen the CHP in the median near the Round Valley exit waiting for you more than I can count. And don't the signs near Sherwin Summit say 6% grade, trucks use lower gears? -

 

[TrippMe]

Thanks for everyone's comments, really appreciate the information.

TIL that you shouldn't coast in neutral any more!

 

[mav_kev]

Stop that. You're not saving anything and only exposing yourself to potential mechanical issues.

Read this, for example: https://www.thedrive.com/guides-and-gear/efficient-to-coast-in-neutral

 

[Bohefus]

I was driving home from Mammoth Lakes heading downhill toward Bishop and I'm doing ~80MPH and I put it in neutral to have the engine RPMs still at ~2500.

Am I actually not in neurtral?

The worst thing is when you had to reach into the back seat to grab your phone & take a pic of the gauge cluster while coasting at 85 mph. J/K

 

[Gray Goose]

Appreciate the response!

Wouldn't towing cause the same thing?

Transmission and Engine are not connected fluids wise (at least not when I last knew) so your explanation doesn't make sense to me.

Am I missing something?

I'm not a flat tow expert, but the vehicle being towed is generally off. Not a mechanically comparable situation. And no do not turn off your ignition while going downhill.

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