Citroen c5 110 HDi Automatic gear change issue?

[trevsw]

I have a very small issue with my gearbox - on cold start the first gearchange between 1st and 2nd seems to over rev a little. this isnt noticable when driving on the flat but i live on a hill and sometimes it is like it has been knocked out of gear and then back in to 2nd gear?

i have no other issues with gear changes and all other 1st to 2nd gear changes are fine for the rest of the day.

thanks

Trevor

[Mandrake]

If the gearbox is a 4HP20 (which I believe it is, off the top of my head) then holding the revs when cold is perfectly normal behaviour.

The ECU is programmed so that a cold start when the gearbox oil is below a certain temperature (a few degrees above zero) results in 1st gear being held up to around 3000-3500 rpm even with a light throttle. This behaviour lasts for around 2-3 minutes and the stated purpose of it is to get the catalytic converter up to temperature quicker in cold conditions to reduce emissions.

I suspect the higher rpm is also used to help get the oil in the gearbox warmed up and circulating more quickly too so that it's not trying to operate with the oil pump running at a low rpm with very thick cold oil...

Nothing to worry about.