went to Carolina over weekend, foothills of the Blue Ridge.

we've lived that area all my life, so i know the roads well. mom & dad live ~hour apart, and both of them expect me to be at their house instantly.

as usual, i was blowing coal and sucking earth, and i use my cruise.

so as i was topping steep little hills with cruise on 65mph, it would not anticipate the top of the hill, and the cruise would hold the pedal down over the top of the hill, and i would be doing 70~75 down otherside,

and the tranny would kick out of overdrive into 3rd, and slow the truck down to ~65mph,

just in time for the bottom of the next hill

 

That's what cruise does. I live in the same area you're talking about but, rarely have a chance to use the cruise. There's just way to many hills and turns.

I wouldn't say you have a " grade brake ". Cruise is just keeping your truck at the speed you set it at. You're carrying a lot of weight so, it's going to increase speed down a hill but, the cruise will eventually level it out.

 

Put the transmission in tow/haul mode.

 

This where you notice one of the advantages of a jake brake.... or the tow/haul mode.

 

I've seen it do it in tow/haul, and i sometimes do that coming down an off ramp. that's what i would think of as "grade braking" when you let off the gas, the tranny drops gears and slows you down.

but I don't think i have ever seen the cruise control drop the tranny a gear to SLOW the truck, and sure i have not seen it do it in normal mode.

just wondering what the parameters are for the cruise to request a gear drop to keep from overspeed? 10mph over what cruise is set to? 15mph?

i might have had the cruise on 65, topped a hill, and got up to 75mph without knowing - some lonely roads out there between the peach orchards.

 

IIRC, if actual speed exceeds set speed by about 3-4 MPH, the trans will kick down to slow the vehicle. At least that's the way it worked on all my cars and my '04 2500 Hemi.

 

Wifes Hemi Durango does the same thing. Kinda freaked me out the first time I noticed it.....

 

I've noticed this a little and sometimes will use cancel then resume when I am getting back down to the initial speed on the upswing so that it will be at what should be a full defuel all the way down I've noticed little better milage when 'driving by cruise' rather than 'set n go'. When moderatly empty (less than 1000lb cargo/people/etc) and in OD it seems to rarely go over 75 on gravity pull. I usually drive right on 68-72