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Ok.
I did a 600km round trip today in much hillier terrain than my usual trips up to Perth and back,or down to Albany back travelling Albany Hwy.
Im convinced the issue of slowing into hills is a 6 speed issue.I paid close attention to how mine worked,very impressed.For those that know WA,I travelled to Bailingup via Collie,Donnybrook,then back up to Bunbury,up to Collie and back to Williams.
There are lots of big hills on this journey,the biggest drop I saw and only on 3 different hills was a 3kmh loss of speed.In 100kmh zones mostly on the journey,I found it easily drops to 99kmh,the ecu usualy gets it without a downshift and seemed to get to 101 or 102kmh uphill.Now on the steeper hills,at 99kmh if it senses its struggling it gives you 7th,that change is really un-noticable,except for the change in revs on the gauge.7th gets you up pretty steep hills,if anybody knows Roelands Hill going up to Collie,it only used 7th on the first pinch near the lookout bay,8th the rest of the way until the roadworks at the top.Thats a 100kmh speed zone.
On steeper hills where it droped the 3kmh it grabs 7th then almost straight away it grabs 6th.You certainly know when 6th is engaged as it rapidly accalerates back to 102kmh then holds 6th for a short time,then 7th and 8th reasonably quickly.It would be interesting to data log a 6 speed and an 8 speed on similar terrain with a Nanocom or similar.
Downhill.No more riding the brakes for me.Steep declines at 100kmh,leave the cruise on,paddle - once,it selects 6th and holds the speed easily.In 80kmh zones on very steep declines into towns,paddle - once gives you 5th,it holds the speed perfectly.
Most impressed,and it returned a 9.1l/100km indicated for the trip.Remember mine is a TDV6 so the SDV6 should be better.
Andrew
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It is not the 6-speed gearbox that is the cause of the loss of speed, rather that LR changed the logic with the introduction of the 8-speed most likely because the higher gearing of the 8-speed and the availability of 7th that is still higher ratio than the 6-speed's 6th makes the vehicle generally more economical so the extra fuel used to maintain speed on hills doesn't affect the overall economy as much. LR announced that the 8-speed was fitted to the 4.4 TDV8 in the 2011 L322 to reduce fuel consumption and emissions.
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Mine's a six speed and, if anything, I find that it accelerates on hills when the cruise control is on - I'm usually doing a couple of km/hr above the set point by the time I go over the top of the hill. Speed will drop to around 1 km/hr below the set point going down a long hill. Some of the hills between Northam and Perth are a pretty good test for the system. ;)
In general, I find that the cruise control is pretty accurate on mine - usually sits on exactly the set point under most conditions, and any variation from this is only ever 1 or 2 km/hr at the most. Even towing doesn't seem to have any affect on it - though I have never towed anything really heavy with the D4.
The only time that I notice any greater variation from the set point is when I hit "resume" after slowing for a town for example. Vehicle will accelerate to about 3 or 4 km/hr above the set point before settling back to desired speed - but I have had plenty of other vehicles that did this (V8 Dunnydoor wagon was a classic for over-speeding on resumption of cruise control), so I've never seen it as a problem.
