AL4 characteristics in 2004 C5 Petrol

[mlkey]

Hello everyone,

This question is ideally aimed at any C5 2.0i petrol auto drivers, but I am also interested in any other vehicles using the AL4 transmission.

When driving the car gently, pulling away with light throttle, it changes into 2nd at around 10mph with the converter still unlocked. I continue to accelerate and at about 25mph the converter is locked bringing the RPM down a little. At 30mph the transmission changes to 3rd and then 4th at around 40mph, both of these changes are with the converter locked.

If I repeat the above while accelerating a little harder, the transmission changes to 2nd and then locks the converter almost immediately before changing to 3rd, it just sounds a bit peculiar. I am not suggesting there is anything wrong, although there could be as I have not experienced other AL4's.

My question is, do others with this transmission experience this same weird 2nd gear behaviour?

Thanks.

[addo]

That all sounds fairly normal (to me, anyhow - my Xantia has a C5 trans in it).

[Clogzz]

Mine does like that too, so say it’s normal.
If it starts changing to 3rd and 4th unlocked at light throttle, it will be caused by the fluid being a bit low.

[mlkey]

Thanks for the replies so far.

Clogzz, most of the time it is fine but there is a section of fast road where I have to jump 3 lanes of traffic. Sometimes I have to give it a lot of throttle while it is still warming up. Occasionally the converter unlocks for perhaps a mile at which point it locks again. This only ever seems to happen while warming up. I did a double flush oil change last spring, and will be doing it again in the next few weeks.

I was very careful to check the oil using the correct procedure. It also hangs onto 1st gear during the first gear change of the day and even with throttle backed off in anticipation of the gear change, it is still quite harsh. Once that is out of the way the gearbox quickly settles down.

[Clogzz]

I did a double flush two years ago and it replaced 75% of the oil.
If you do another flush soon, you will throw out 87.5% of the oil you put in last year.

My box is shocking when cold, and it doesn’t get cold here.
It locks and unlocks second, and also unlocks third when pushed, until it’s warmed up.
It goes to fourth at 65 km/h and stays there even when slowing down to 1100 rpm.
After warm-up, it behaves properly.

Even when warm, when slowing down to unlocked second, then accelerate, nothing happens for about two seconds, as if it was wondering whether to downshift to first.
That’s at intersection creeping speed and is outright dangerous.

The car came with a dim ‘3’ on the gear display, as if the previous owner was in the habit of mostly driving in third gear to prevent all that gear changing.

[mlkey]

Hi Clogzz,

Thanks again for your reply. As frustrating as your answers are, I take some comfort that we either have the exact same faults, or the exact same design flaws. You describe all the things I have noticed perfectly, even the dangerous delay when not quite stopped and trying to accelerate away. I have largely adapted my driving to cover these things, not pushing too hard when the engine is warming up, and even using both feet on the pedals at junctions, have to be careful with this though as too long on both pedals can shut the throttle down for a few seconds.

I tow a caravan which is why I will do the oil changes every year. Thanks again for the feedback, I will learn to live with it until I change my car.

[CitroJim]

even the dangerous delay when not quite stopped and trying to accelerate away.

That's a 'feature' of the 4HP20 too It can vary by 'box. Some are good and others are not so good. I believe the logic controlling the gearbox gets it's electronic knickers in a bit of a twist and wonders just what to do. It wasn't expecting you to want to take off again after looking as if you were coming to a halt and goes a bit wobbly for a second as a result.

This is the problem generally with what is an early version of the 'fuzzy logic' used to predict the gears/lockup regime required at any given time. In fact, as much as I love the 4HP20 it does have some rough edges and it looks like the AL4 has much the same rough edges too. All because the 'fuzzy logic' is trying too hard to be clever. Mostly it succeeds but at times it really shows it hasn't a clue

Drive an older completely hydro-mechanical autobox and see the difference. It's staggering. They're as smooth as a bar of Galaxy

Against that though, no hydro-mechanical box can give the same level of performance and economy as an auto-adaptive. Nor give the same kick-down performance or the fun of a sport button!