2010/late 3.6 TDV8 L322 with ZF6HP box and adaptive cruise control.

When cruising on the motorway in cruise control it kicksdown from 6th to 5th at the slightest hint of an incline and/or if I request an increase in speed via the steering wheel.

Out of cruise control it will stay in 6th when accelerateing/maintaining speed on hills, with it kicking down only when demanding lots of throttle.

Gearbox is high mileage (160k) but serviced, and megaflushed by Bodsy earlier this year.

Is this a standard characteristic of this gearbox behaviour when in CC?

I have the same gearbox as you and yes, this does happen (very annoying). I usually end up sticking box into manual. Must remember to put back into auto when slowing down, coming off at a junction, as can get caught in a lower gear inadvertently. Previous cars:
S-Max 2007-2013 (only diesel I've had, good car but expensive when diesely bits go wrong, so what's the point?)
Galaxy 2001-2007
Mondeo Estate 1997-2001
Sierra Estate 1993-1997
Uno Turbo 1987 -1993
Fiesta 1984 - 1987
Fiat 127 1982 - 1984

I have the 4.4 TDv8 and it does the same thing, it will drop down a couple of gears sometimes just to pick up say 15mph which it could easily do without changing gear at all. 2011 Range Rover Autobiography TDV8 Buckingham Blue

With my 4.4 if I don't want to use manual mode to prevent the downshifts but I think that it might downshift on a rise then I'll press the upshift paddle for temporary command-shift mode which will be maintained until the gearbox doesn't feel the need to downshift by reverting to full auto mode.

I found that the down-shifts occurred more readily after converting from standard CC to adaptive CC. With standard CC the gearbox didn't down-shift early enough so dropped 2-3 gears. At least with ACC it will only drop from 8th to 7th initially.

Thanks. This is the 3.6TDV8 with the 6 speed box.

appj62 wrote:

I have the same gearbox as you and yes, this does happen (very annoying). I usually end up sticking box into manual. Must remember to put back into auto when slowing down, coming off at a junction, as can get caught in a lower gear inadvertently.

Had the ZF6sp on my old audi A6 Quattro and it did the same but it never particularly bothered me. My ZF8 holds gears too long on hills IMO so I often use the paddles to change up - not sure if the gearbox is sensing extra load or it's getting an input from the body control system that it's on a hill? It holds gears under acceleration on the flat pretty well without dropping down. Worth on either box checking you have the latest gearbox software update. Also if you have a bigger tyre aspect ratio than stock this will change gear change behaviour. 2012 TDV8 Vogue (L322)

I was toying with also asking this. Wasn’t sure if this was normal. Good to know, albeit unnecessarily eager!

Also interesting that the 8spd in the 4.4 is equally eager.

Having driven today towing a trailer from foggy Herefordshire to sunny Reading and back I put the instant fuel on the screen (very scary by the way) and tried leaving it full auto and knocking it in 6th and leave it there. According to the car there is very little difference in fuel economy between auto and leaving in top, quite counter intuitive I know but I will leave it in auto now and let it get on with it, driving without a trailer will be easier on the engine and might well work, but I will leave it to do it's thing.
Somewhere there is an Arab with a spring in his step and will be extracting more stuff out of the ground to replenish what has been used today.

Thanks all, looks like this over-eagerness to kickdown when in cruise control is a characteristic of the way they've calibrated the car then.

I shall continue knocking the lever over to manual 6th gear when on long motorway cruises!