Shifting into neutral

[mkriedel78]

Hi everyone,

I'm fairly certain this is "normal," but since diesel trucks are new to me, I figured I'd ask.

I have a 2008 Chevy Silverado 3500 Duramax w/ the 6-speed Allison transmission.

Last night, I was driving home at about 60-65 mph down a very slight grade, but downhill nonetheless. I was not towing or anything like that, just driving.

So, while in drive with my foot off the accelerator, my RPMS were in the 900-1000 RPM range. When I shifted into neutral, however, the RPMs went up to ~1200-1400.

This surprised me, as any other automatic I've ever owned, shifting into neutral brought the RPMs down to idle speed.

It didn't seem to hurt anything, and I just shifted back into Drive and carried on. I just want to know if that's, indeed, 'normal' behavior in a truck like this.

Thanks!
Matt

[coolbreeze01]

A long time ago, I remember putting equipment in neutral on long straight downhills. Once the high-speed bounce passed, it was fun.

[wilber1]

Cyberian wrote:
Even illegal in Canukistan

Ya'll do whatever you're going to do. Try not to kill anyone else in the process, eh?

I don't know what your problem is. No one has suggested making a practice of coasting down hills in neutral. One person posted that if engine braking is giving you control problems in very slippery conditions, try putting the vehicle in neutral so the brakes can do their work without interference from the engine. You then start flaming them and calling people idiots.

There comes a point whenever we stop a vehicle that the engine stops providing braking and starts to try and push the car. It has to in order to keep from stalling. Normally we don't notice this with an automatic because the torque converter won't let the engine stall. The engine is still trying to push the car but the tires have enough traction to prevent it. This can be a problem when driving on ice in traffic. If it is a problem, put the car in neutral so the engine isn't interfering with the brake system. This is not rocket science, a person driving a manual does it every time they come to a stop. That is what a clutch does, disconnect the engine from the drive axles.

Bottom line, the only real idiot is the one that doesn't do whatever it takes to control their vehicle.

[jaycocamprs]

deleat

[Cyberian]

Even illegal in Canukistan

Ya'll do whatever you're going to do. Try not to kill anyone else in the process, eh?

[davisenvy]

Here's food for thought. Anyone ever drive a straight shift and take too long shifting gears on the interstate? Or even miss a gear and were coasting in N? Press in the clutch to come to a stop? Or do you have perfect heel/toe action to perfectly match the rpm's on a downshift? I honestly don't see what the big deal is. If it was that dangerous, don't you think auto makers would make it impossible to shift into N while moving?

[wilber1]

Cyberian wrote:

wilber1 wrote:
What you say about cruise and the ebrake is true but the principle is the same.

Front brakes wear faster because most front engine vehicles carry more weight up front and under braking, weight shifts off the back to the front. That's why front brakes are much larger than rears.

Unless the front of the car somehow comes detached from the rear, engine braking helps both sets of brakes. Both sets are stopping the same vehicle after all.

I'm not suggesting one should put a vehicle in neutral at speed but if you are trying to come to a stop on a downhill in very slippery conditions, you will not be able to do it in a RWD non ABS vehicle without locking the front brakes unless you put it in neutral. Those back wheels will keep on turning with the fronts locked or you will have to lock all four.

How exactly does engine braking help slow the front axle if not in 4WD?

Both my Dodges (2500 diesel 4x4 48re '03 and '07) the front and rear disks are the same size.

Did you not drive in winter up there back when just about everything was RWD or a clunky 4WD with front disks, drum rears, and no ABS? Did you spend eternity skidding?

Why am I wasting my time with this?

You aren't slowing the axle, you are slowing the vehicle. You can quit wasting my time any time you like.

[Cyberian]

wilber1 wrote:
What you say about cruise and the ebrake is true but the principle is the same.

Front brakes wear faster because most front engine vehicles carry more weight up front and under braking, weight shifts off the back to the front. That's why front brakes are much larger than rears.

Unless the front of the car somehow comes detached from the rear, engine braking helps both sets of brakes. Both sets are stopping the same vehicle after all.

I'm not suggesting one should put a vehicle in neutral at speed but if you are trying to come to a stop on a downhill in very slippery conditions, you will not be able to do it in a RWD non ABS vehicle without locking the front brakes unless you put it in neutral. Those back wheels will keep on turning with the fronts locked or you will have to lock all four.

How exactly does engine braking help slow the front axle if not in 4WD?

Both my Dodges (2500 diesel 4x4 48re '03 and '07) the front and rear disks are the same size.

Did you not drive in winter up there back when just about everything was RWD or a clunky 4WD with front disks, drum rears, and no ABS? Did you spend eternity skidding?

Why am I wasting my time with this?

[MitchF150]

So did anybody ANSWER the OP's question?

No.. He found the answer himself from another source, but there was one poster that did mention that it could be the computer raising the rpms to match the speed so when it's shifted back into gear, the engine speed would be better matched to the vehicle speed... I've never heard that before, but it got off topic to the whole 'snow' deal pretty early and wilber likes to put it in neutral and others don't... 😉 That's the "topic" now... 🙂

Mitch

[wnjj]

Cuffs054 wrote:
So did anybody ANSWER the OP's question?

Yeah, he did. 😉

[Cuffs054]

MK, thank God you have decided to stop doing this! The chance that you could upset the time/space continuam is just too much to fool with. So did anybody ANSWER the OP's question?

[wilber1]

Cyberian wrote:

wilber1 wrote:

Cyberian wrote:
Doesn't matter. ABS, 2wd, 4wd, duals, 10 wheeler, 18 wheeler, any vehicle with locked brakes is nearly uncontrollable. Putting your transmission in neutral removes a crucial element of control and increases the likelyhood of locking your brakes.

Yes any vehicle with locked brakes is almost uncontrollable and if the rear brakes need extra pressure to override the engine, the greater the likelihood you will lock the fronts in the attempt. Basically the same reason manufacturers emphasize not to use cruise control or the exhaust brake in slippery conditions, you wind up with the wrong end steering the vehicle.

Cruise powers your rear into slides, Jakes brake the rear axle too much and cause slides. Your drive axle is already trying to slow more than the steer axle when you release the throttle due to engine braking. Ever notice that on RWD vehicles, the front brakes always wear out sooner than the rears? It's because native engine braking is helping the rear brakes!

Override engine power in order to slow the vehicle...sure, if one's right foot were on the throttle and left foot on the brakes.

The only time any vehicle should be in neutral with the engine running is while parked on a level surface with the parking brake set and tires chocked.

What you say about cruise and the ebrake is true but the principle is the same.

Front brakes wear faster because most front engine vehicles carry more weight up front and under braking, weight shifts off the back to the front. That's why front brakes are much larger than rears.

Unless the front of the car somehow comes detached from the rear, engine braking helps both sets of brakes. Both sets are stopping the same vehicle after all.

I'm not suggesting one should put a vehicle in neutral at speed but if you are trying to come to a stop on a downhill in very slippery conditions, you will not be able to do it in a RWD non ABS vehicle without locking the front brakes unless you put it in neutral. Those back wheels will keep on turning with the fronts locked or you will have to lock all four.

[JJ_Spectre]

davisenvy wrote:
I bet you guys don't remove the tag off your mattress either.

Outstanding!

We need a quote of the week thread, LOL.

[Cyberian]

davisenvy wrote:
I can't believe all the ninny responses to this. I bet you guys don't remove the tag off your mattress either. You better not or else the flux capacitor will overload flipping world into reverse orbit. It is also against the law to whistle under water in Vermont.
Wilber1, I'm with you on this.

You know, Darwin had a point.

I can't believe any of you seriously advocate putting it in neutral.

Dumbest thing I've heard in years.

[45Ricochet]

mkriedel78 wrote:
Hi Everyone...

Thanks(?) for all the replies. I was kind of hoping someone with this actual truck who's done this before would chime in. I didn't realize quite the can of worms I was opening when I asked.

Regardless, I found this elsewhere:

Another neat trick is that if you're going down the road and you shift into neutral, the engine wont drop down to idle...the TCM has whats called "neutral tracking", meaning it will automatically raise the engine speed to the proper "rev-matched" speed, so when you move the shifter back into drive, the engagement from neutral to drive at X mph will be smooth and rev-matched so theres no huge clunk.

Source

So, it does in fact seem that it's supposed to do this.

Thanks for everyone's concern. I'll stop being public highway enemy number one now, and leave it in drive. 😉

Opening a can of worms is not to hard on this forum :W
Interesting information with the RPM. I suppose if you were doing 80 MPH your tack would be even higher then :H I did think of that afterwards, that low idle RPM would be a killer on the TC when you did shift back to drive , thus the big CLUNK.
Interesting but lets just say I ain't going to try it out for an example for this forum :B Heck my Cummins always feels like it's in neutral down hill without the exhaust brake on without a manual downshift, even then it's weak at engine braking without the EB.

[ExxWhy]

Wow, did this thread go off the rails!