Autobox kickdown

[swiveleyedgit]

Evening all. Now I may or may not have a problem with the gearbox in my C5, as far as I can remember this quirk has always happened ever since I've had the car, just over a year now. What happens is I'll be cruising along a motorway for instance doing 70 or 80 and if I just squeeze the throttle slightly the box will invariably change down into third gear as if I've floored the pedal. Strangely, it seems to do this only when going uphill, it also does it whether the cruise control is on or off. Now I know that if the cruise is on and you start to climb a hill it will change down when the engine speed starts to slow but I'm assuming that's how it's supposed to work when the cruise is activated. Is this normal for an AL4 box? I'm only talking about a very small increase in throttle position, if I do floor it then the kickdown works as it should.

[xantia_v6]

It is probably normal, the transmission will change down if it thinks that engine efficiency will be better in the lower gear.

[addo]

Yes, exactly.

You notice the same thing on manual cars if you watch the instantaneous consumption figures, it sometimes goes against the grain of what "feels" right.

[swiveleyedgit]

Hmm, I've never had an autobox that changes down at 80 mph when you just press the throttle a touch. The car doesn't actually accelerate much anyway, just makes a lot of noise, is there any diagnostics for this on Lexia? I might plug the laptop in...

[Mandrake]

Is it in sport mode ?

Also what engine RPM is it doing just before and just after it goes down a gear ?

[octo0072000]

My new to me C5 2004 110hdi auto is the other way no kick down every thing else works as it should works all ok in manual mode not using sport mode but seems to work dash lights work
think my problem is too much free play on the throttle cable having a look tomorrow
any input welcome

[swiveleyedgit]

My new to me C5 2004 110hdi auto is the other way no kick down every thing else works as it should works all ok in manual mode not using sport mode but seems to work dash lights work
think my problem is too much free play on the throttle cable having a look tomorrow
any input welcome

My C5 was the same when I first got it, there was loads of free play at the pedal. I managed to adjust it without taking half of the engine bay out....

As to my own gearbox foibles, after reading Mandrake's post I've tried driving with the sport mode on but it it doesn't seem to make any difference, I'm positive that it only happens when going up an incline, it doesn't have to be steep either.

[octo0072000]

swiveleyedgit

when does yours go into lock up top gear mines seems to be at about 50mph

[swiveleyedgit]

swiveleyedgit

when does yours go into lock up top gear mines seems to be at about 50mph

It changes from 3rd to 4th at around 50 mph, haven't noticed that it locks up as such in 4th, it doesn't slip like 2nd and 3rd gear and then lock up as the revs rise.

[octo0072000]

little update sorted kickdown out was too much free play on cable
and no need to pull the fuse box to get to it you can get into it by removing the air filter/box and fusebox cover and strut cover
you can see the cable through the air box side and adjust the cable with one hand down between the strut top and fuse box other hand by the airbox bit of a fiddle but easy doable
thanks to swiveleyedgit
my gearbox changes up the same as yours so all seems ok