Cruise control error on GMT900

[Wires]

I'm finding when I set the cruise on my 08 SD (6.2L/6speed), it's fine on fairly flat land, but it NEVER holds speed on rolling hills.

 

If I set it for 105kph, it'll hit 100-103kph climbing a hill, and then start to accelerate. Once it crests, it doesn't stop until it's at 108-110kph.

 

There seems to be a huge deadband in operation.

 

Anyone else have this? What I don't know is if it's amplified by the Westers tune, or if it's really that bad. My GMT800 was pretty close to bang on the setting.

[nickvrebel]

sounds like normal operation to me. Where I live it's completely flat, but I frequently travel Hwy 61 North in to Ms. and it's rolling hills and I get that much speed variation. The slow down is because the truck is trying to resist downshifting (then you would complain that it downshits too much), it over accelerates because it's over compensating, the truck is keeping the throttle up to make sure it's not just a momentary break in the grade (or a tail wind...or....).

[jandersinc]

I can set mine at 55 mph, it'll hold that speed (or close to it) going up but I can be 65-70 mph at the bottom of the other side.

[Wires]

sounds like normal operation to me. Where I live it's completely flat, but I frequently travel Hwy 61 North in to Ms. and it's rolling hills and I get that much speed variation. The slow down is because the truck is trying to resist downshifting (then you would complain that it downshits too much), it over accelerates because it's over compensating, the truck is keeping the throttle up to make sure it's not just a momentary break in the grade (or a tail wind...or....).

 

 

Thanks for the confirmation. Just wondering. Most of my trips are pretty flat, so it typically doesn't show up. And other times on those hills, traffic was too erratic to use cruise (except for a couple of weeks ago).