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

[2oldman]

I would think the rpm would be idle. Interesting...

[Cuffs054]

Geez guys, it's a little late for the way. And I'm sure all of us have "tried" something to see what happens. I'm kinda interested in the answer. My guess would be that the engine speed was being retarded by the drive train in gear, but why RPM went in neutral is interesting. It would help to know if the revs stayed that high or went down.

[Turtle_n_Peeps]

I guess my first question is why would you do this? :h

I have no idea if it's normal or not because I have never done this or ever will.

My guess would be since the engine has a fuel cut off (accentually the engine is cut off from fuel and the torque converter locks to keep it turning over) the puter told the injectors to give it fuel to keep running.

[Jim-Linda]

Why would you shift into neutral going downhill?

Jim