• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Cruise control

GT_80

Full Member
Joined
Mar 17, 2014
Messages
305
Location
North Central Massachusetts
I use my cruise control a lot, but one thing that seems weird is that when I'm coasting down a hill it feels like the truck is applying the brakes so I don't go over my cruise speed- Is that a feature?
 
Not on mine.

I have a two-lane highway I travel from time to time that has a pretty good drop toward the valley floor between two hills.

I run with the cruise all the way from one end to the other.

As I go down one side, my speed will go up 10 to 20 MPH over my set speed.

As I head up the other side, the truck will slow down until the cruise takes over and maintains my set speed up the hill.

I sometimes have to apply my brakes on the downhill leg if there is traffic ahead of me.

If no traffic, I let 'er fly.
 
The truck is not applying the brakes but the engine's RPMs go down and the transmission slows you down until you get to cruise speed. Unlike a manual transmission vehicle, our trucks stay in gear all the time (unless you put it in neutral) so whether you're going down a grade or on level road, the moment your foot is off the gas pedal the vehicle starts to slow down incrementally. A manual transmission vehicle however will gain momentum going downhill if the clutch is disengaged. It's not the same for ours.

Now if you're coasting down a hill and you're not facing where you're going, your cruise control will be the least of your worries.  :laugh:
Apologies I just had to make a joke.
 
Dluvr22 said:
The truck is not applying the brakes but the engine's RPMs go down and the transmission slows you down until you get to cruise speed. Unlike a manual transmission vehicle, our trucks stay in gear all the time (unless you put it in neutral) so whether you're going down a grade or on level road, the moment your foot is off the gas pedal the vehicle starts to slow down incrementally. A manual transmission vehicle however will gain momentum going downhill if the clutch is disengaged. It's not the same for ours.

Now if you're coasting down a hill and you're not facing where you're going, your cruise control will be the least of your worries.  :laugh:
Apologies I just had to make a joke.

I am very familiar with cruise in automatic vehicles- My 2003 Sierra that I owned for 3 years just prior to this truck had basically the same setup- It had a 4.8L LS motor, 4L60E transmission, with 3.73 gears, 4wd and it never did the choppy downhill thing... I have only had the Avy for 7 months, and I often have a sinking feeling that I bought a lemon. It's nice enough that I want to keep it and keep working on it, but at the same time, I bought a car with a loan because I thought I wouldn't have to work on it all the time...
 
You might want to make sure you don't have a brake dragging or maybe a hub bearing going out and dragging.
 
Randy said:
You might want to make sure you don't have a brake dragging or maybe a hub bearing going out and dragging.

I've had all the brakes apart, and no noticeable weird wear- the front wheel bearings have both bsd in the last 8 montheen change
 
Actually that is how your cruise control is designed, it cuts power to the engine to get it back to the set speed.

Good thing if you have the DIC set to Inst Econ( Instant Economy ) you will see it's getting 58 MPG
 
I think what he is saying is it does not coast and pick up speed  on a down hill run like his old truck with basically the same drive train. Could be just differant tunes, aerodynamics, weight etc..
 
I just wonder if a 2003 Sierra was drive by wire. ???
I read his old post.

Sierra = truck   Avalanche = SUV apples vs oranges
 
MS03 2500 said:
I just wonder if a 2003 Sierra was drive by wire. ???
I read his old post.

Sierra = truck   Avalanche = SUV apples vs oranges

I'm starting to find that out... I believe my Sierra was drive by wire, same as the Avy... It has the same intake, same (looking) throttle setup.

The differences I see between the two are: Gear ratio (4.10 versus 3.73), Trans tune (old trans in Sierra shifted way harder than the one in the AVY), Open diff versus gov-loc. Apparently the computers have to be different-

I was talking to my brother who does performance GM tuning and he thought it might have to do with the computer tune or the torque converter.

Someone mentioned the brakes dragging- It can't be that- if it was, the same effect would happen when I did not have the cruise on and coast down hills... If I do not have cruise on and I coast down a hill, the symptom does not present itself. So either the motor is cutting power on down hill, or its something with the cruise changing something in the trans. I don't know- its annoying.
 
enoniam said:
Can you describe "the choppy downhill thing"?

feels like the truck it applying the brakes once a second to maintain the speed. It doesn't "coast"- the speed will stay at the set rate no matter if I'm going down a hill or not. But only when my cruise is on
 
I'm pretty sure that is all it is, even with my 2500 acts different than a 1500.

In Michigan when I caravan with members with 1500s and get to a hill, going down a hill I have to ride the brake cause it will not slow down.
 
MS03 2500 said:
I'm pretty sure that is all it is, even with my 2500 acts different than a 1500.

In Michigan when I caravan with members with 1500s and get to a hill, going down a hill I have to ride the brake cause it will not slow down.

Mine does slow down though- first one ever.
 
I'm about a thousand pound heavier than a 1500 so take may be it.


On a side note I was at the Power Tour 2012 and it was at the GM Proving Grounds they let us take the cars on the test track, there was a 40 degree high banked turn  following into a tunnel I slowed down to let traffic get waaaay ahead of me and nailed it. LOL what happened next scared me senseless. I shot out the tunnel like a cannonball.
 
Back
Top