Thread: D4 Cruise Control

Craig - interesting that you've raised this, as just the other day I noticed that I'd crept up to 4 kph over over the set speed going down a hill, and this was unusual as mine has kept pretty much to the +/- 2 kph variance since new. Not a particularly massive hill, and one that I regularly drive - so nothing new there. Have not noticed any significant drop off on the down side yet. I know Graeme's bus was showing more variation early on - be interested to see what his situation is now.

Mine hasn't changed and thus still can't be trusted in hilly terrain. I find quite annoying when lots of other vehicles can keep a constant speed and I am forever adjusting mine. I cancel at 4 kph over because of the likelihood of going a lot higher. Cancelling totally cuts fuel whereas overrun does not.

I have never used a cruise control that holds the set speed on a reasonable descent. A slight incline yes, but not a descent sized hill. I know a lot of the heavier truck transmissions, and even some of the 'Allisons' fitted to the big Chevy Silverado's, have a sophisticated enough setup to hold the set speed, even with a load on the back ( like a caravan ) on any downhill slope.

The D4 is no different to the others ( in my experience ). I think your expectation is a little high.

It seems that the D4 allows the slight de-acceleration of approx 4km while going uphill which actually avoids the abrupt changedown I have experienced with previous vehicles. Its appears to be more intuitive in uphill with the downhill being related to momentum more than acceleration.

Sounds like it is a common fault with the D4. My D3 was always within 1...maybe 2Kph up and down hills.
Discojools commented that his D3 was all over the place, whereas his D4 cruise is great.
Does anyone know whether this fluctaution can be adjusted?
Cheers, Craig

My D4 3.0L has always been shocking on cruise control on anything but the most level of roads. I made comment on another thread that it was by far the worst out of all the cars I've owned.

With the 'smarts' the car has, the 6 speed box and the 600Nms of torque....there really isn't any excuse.

My 2.7 D4 is a shocker on cruise also. I appreciate the fact that the 6 speed doesn't kick down aggressively to maintain speed however more often than not it shouldn't need to anyway as it has enough grunt to maintain the speed as proved by manually (without cruise set) attacking the same incline.

Mine drops approximately 6kph before it seems to realise it's no longer doing the speed selected and apply more throttle, or then kick down because it has slowed so much that it is now out of the torque band.... quite frustrating really. My manual diesel Jeep was great in comparison if not a little aggressive with it's response.

On the flat and when the engine loads up a bit up hills my RRS is able to hold speed very well - normally within 1kph but going downhill is a different matter. The car runs on very easily suppose is is reasonable aerodynamics and its considerable weight but it also does this on cruise control - going downhill I have been up to 20kph over the speed set.

The cruise control is obviously a very basic system simply opening and closing the throttle - I would have thought that given the price of the car the system would have been a bit smarter - maybe even feathering the brakes to minimise over run.

Garry