C5 Automatic transmission

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David290361
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C5 Automatic transmission

Post by David290361 »

Hi all,
New member here. I did a search but didn't get any appropriate matches.
I recently purchased a used 2009 C5 2.7 litre exclusive sedan. This is my third Citroen after a 1220 GS Club which I purchased many years ago in Berkshire and a new 2.0 l HDI C5 in around 2003.

I noticed that the transmission shifts up at around 2000rpm under light throttle application and at higher rpm under heavier throttle.

I now notice that just after a gear change, if I depress the accelerator further the engine rpm increases without a noticeable increase in vehicle speed, almost as if it were a CVT transmission.

Is this normal or should I have it seen to?

I plan to drive the car across the Nullarbor(ing) to Sydney, a distance of over 4000 km. It would cost more than the car is worth to have it towed should it break down.
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Mandrake
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Re: C5 Automatic transmission

Post by Mandrake »

Is that a petrol or diesel ? I'm guessing its a V6 diesel, as I believe all the PSA petrol V6's are 3.0 litre ?

Either way, shifting up to the next gear at 2000 rpm under a light throttle doesn't sound unusual for a V6 - my 3 litre Xantia V6 petrol Auto will shift up to 2nd then 3rd at about 2000 rpm if I pull away from the lights gently...if I accelerate harder it will of course hold the gear higher.

Your second remark about the engine rpm increasing without much road speed increase if you squeeze the throttle just after a gear change also doesn't sound unusual, depending on the exact conditions that it happened under.

Modern Auto boxes have computer controlled torque converter clutch lockup, and they're constantly deciding whether the torque converter should be open (as in an old fashioned auto where it was always open except in top gear) or closed, or transitioning between the two.

When the clutch is open you get up to 800 rpm of slip across the torque converter, but also get torque multiplication, and in this condition if you go from a light throttle then accelerate you will hear the engine rpm rise about 500 rpm immediately, before the car starts to accelerate.

When the clutch is closed it will feel basically like a manual where there is no slip and a one to one correspondence between engine rpm and road speed - there will be an instant road speed change in response to throttle. It can be a bit disconcerting that sometimes the gearbox feels like an auto and sometimes it feels more like a manual, but that's the way many modern auto boxes behave.

If you accelerate quickly through the gears from a standstill its normal for the torque converter to remain open in lower gears to provide torque multiplication and maximum launch acceleration, in that case if it changes up to 2nd on a light to moderate throttle and you then squeeze the throttle the rpm will increase suddenly with a delayed increase in road speed as you describe because the torque converter is still open.

However if you speed up until it changes into 2nd then linger there at the same speed for a few seconds many gearboxes (at least the Xantia box does) will then transition the clutch to a locked up state to improve fuel economy. If you know what you're looking for you can notice the transition. Now if you give it some extra throttle it will accelerate without a large initial rpm increase, just like a manual. Confusing isn't it ?

Also under some conditions where the clutch is already locked up enough throttle will trigger the clutch to unlock - for example if I'm cruising at 60mph in 4th and press the throttle down about half way the torque converter will unlock and the rpm will immediately increase about 500 rpm without any initial change in road speed - it feels almost like a down change to a lower gear but its not. The open torque converter provides torque multiplication to increase acceleration at the expense of a delay. (And increased fuel consumption)

If I press the throttle down further it will then actually change down a gear and the rpm will increase further. The torque converter clutch opening in these conditions is used almost like a "half" down change in gear.

I'm not familiar with the specific box in your car (hopefully someone who owns one will reply - I'm sure we have at least one forum member with that model of gearbox) but I don't see anything to worry about in what you describe about the gearbox. If its a diesel its even more likely to shift up at what seems like very low rpm since the power band on a diesel V6 is lower down than a petrol V6.

However if you are going to do 4000km through the middle of nowhere I would give the car a good general check over and a service before you go! :) It would make me nervous to do that sort of distance in a newly purchased as yet unproven car even with a check over to be honest... Cars take time to gain my trust, but that may be because I only buy old cars! :lol:
Simon

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2016 Nissan Leaf Tekna 30kWh in White

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David290361
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Re: C5 Automatic transmission

Post by David290361 »

Thank you for your very detailed response Simon.

Yes it is an HDI engine. I am not exactly a lead-foot kind of driver, but the type of rpm increase I noticed when I accelerate after a gear change never exceeds 500 rpm.

The vehicle the C5 replaced was a rather under-engined Renault Laguna, 2.0 l petrol, also automatic. I didn't notice that car ever to do the same thing. That vehicle crossed the same stretch of road 3 times in the time that I had it with no drama.

The Citroen has been serviced at the scheduled service intervals, but as these are very generously spaced (20,000km!) I was more concerned if the transmission was "slipping" was I doing it damage. The transmission never appears to slip in 6th gear anyway, only when I gIve it some welly just after it has shifted.

Thanks again for your response.
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Re: C5 Automatic transmission

Post by citroenxm »

I beleve also its an aisn japaneese auto box and not ole faithfull ZFs failure box in these. However I can comment on the character of the box.
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C5 Automatic transmission

Post by mooseshaver »

I think your gearbox sounds the same as mine so you probably shouldn't worry. Unless both of us have dodgy boxes.
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Re: C5 Automatic transmission

Post by NewcastleFalcon »

The 6-speed box fitted to your C5 is most likely to be an Aisin Warner TF-80SC, AF40/6 (six speed). Have to admit mine isbfitted to a Vauxhall Vectra, but its the same box, and is also fitted across a variety of other manufacturers.

Simon's contribution makes very interesting reading. I have probably become a touch sensitive to potential auto gearbox problems, as at a very young 60,000 miles, I had to have an expensive rebuild on my AWTF-80SC auto box. Its now 70,000 miles after the rebuild and the box is still working well. Every slight "flare" (engine revs rising no immediate increase in roadspeed), or harsh change fills me with dread. Simon's contribution has comforted me somewhat. In general the box is very smooth and harsh changes are few and far between.

I suspect the root problem of the gearbox failure was water/antifreeze ingress. I now have an external cooler fitted.

I do have an irrational fear now of driving through puddles/flood water. The first failure loss of drive, slipping, spanner light on, occurred after driving home in a monsoon through many patches of standing water. Now I avoid puddles at all costs, it turned out to be very expensive. Knowing what I know now I think I would have tried a full oil change pretty much instantly. The fault from complete loss of drive resurrected itself by pulling over, a period of rest and switching off and switching on again. It then became an intermittent fault, mostly when warmed up, but became progressively worse over a period of weeks resulting in the rebuild.

My advice If you have an Aisin Warner TF-80SC, AF40/6 (six speed) autobox in your C5 don't drive through standing water!
I would also check that your fluid is also nice and red with no nasty smells. The boxes are "filled for life", but to maximise the life of yur auto box it is probably worthwhile to get a full flush transmission fluid change at some point, using the correct spec fluid.

regards Neil
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Mandrake
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Re: C5 Automatic transmission

Post by Mandrake »

NewcastleFalcon wrote: Simon's contribution makes very interesting reading. I have probably become a touch sensitive to potential auto gearbox problems, as at a very young 60,000 miles, I had to have an expensive rebuild on my AWTF-80SC auto box. Its now 70,000 miles after the rebuild and the box is still working well. Every slight "flare" (engine revs rising no immediate increase in roadspeed), or harsh change fills me with dread. Simon's contribution has comforted me somewhat. In general the box is very smooth and harsh changes are few and far between.
It depends on the nature of the flare up in engine revs as to whether its a worry.

What I was seeing on my old V6 with the worn gearbox was a very brief flare lasting a fraction of a second - for example if I was cruising at 60mph in top gear and pressed the throttle slightly there would be an immediate, audible, but brief flare up of the rpm of about 100-200rpm which would then drop back within about a quarter of a second. If I then pushed the throttle in a bit further I'd get another brief flare up then it would drop back to normal again and so on.

Every time I'd increase the throttle a small amount the rpm would flare up then immediately drop back. I suspect this was due to the worn torque converter clutch slipping before the ECU stepped in to make a correction. On my new V6 I don't see ANY sign of this sort of flare up at all, which gives me more confidence that this behaviour was not normal. The car will simply accelerate in response to a small throttle increase with no sudden rise then drop in rpm, provided the torque converter was already in lockup mode.

However a prolonged rise in rpm of several hundred rpm without an instant increase in road speed in response to a moderate throttle increase is not cause for concern - because most likely the ECU has released the torque converter clutch to provide torque multiplication - the slip goes from less than 50 rpm to about 500-800 rpm before the car will start to accelerate. Or if the torque converter was already unlocked then you have the typical auto box "sloppy acceleration" feel where the engine speed and road speed are decoupled.

Also keep in mind different brands of auto box may not behave the same way so I'm not sure how much my experiences with the 4HP20 can be generalised...
Simon

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Re: C5 Automatic transmission

Post by David290361 »

Thanks all for the replies.

I am now travelling even further as I have decided to take the family on a Tasmanian holiday while I'm over the other side of the country, and of the course the return journey back to the Great Western Sandpit (Western Australia), so its likely to be in excess of 10,000 km by the time we get back home.

I will put the vehicle in for a service a couple of weeks before we leave. The vehicle was purchased a couple of months ago with 80,000km, roughly 50,000 miles, on it. It already has 90,000 now. When I got it it it had an issue with the brake light switch which wasn't telling the ECU when I had my foot on the brakes and was giving spurious alarms of "ParkBrake failure" and other similar alarms. At first I thought Ah ha! battery, so I chucked a new in it and it didn't do it for a couple of days. Of course though it started happening again with monotonous frequency so I took it back to the dealer where it was originally purchased. They were familiar with the car and diagnosed and fixed the problem on the spot.

I am unsure whether the timing belt has been changed, and I'm told that this needs to be done at 100,000 km, so I will have that done at the same time, if necessary.

Incidentally this was why my first C5 was punted: 3 years old and around 30,000 on the clock and it needed a timing belt???
European delivered versions of the same car have 60,000 km intervals on timing belts!

it was a 2.0l HDI of 2003 vintage I think.

This car is an absolute dream to drive: more comfortable than any vehicle I have ever owned. Sunroof, leather, cruise and speed limiter, blue-tooth telephone connection, voice activation (if I use a funny accent - It understands my daughter better than me!)

Once again, thanks for your help.

David.
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Re: C5 Automatic transmission

Post by Mandrake »

I don't know where you got 3 years and 30,000 Km for a timing belt - I've never heard of a car having such low figures ??
Simon

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Re: C5 Automatic transmission

Post by CitroJim »

Enjoy Tasmania David :-D We went there for a holiday in 1992 when we were living up in Darwin. We went to Tas to escape the heat and really fell in love with the pace.

We were reminded just how big Australia was on that trip. It took us all day to fly from Darwin to Hobart via Alice and Adelaide...
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Re: C5 Automatic transmission

Post by David290361 »

Mandrake wrote:I don't know where you got 3 years and 30,000 Km for a timing belt - I've never heard of a car having such low figures ??
Evidently the importer, a firm called Ateco sets this interval. They also now import Fiat which were absent from the market since I was a kid. They may have been nervous about warranty claims. 3 years was the interval they quoted the vehicle had only 30,000 km when it hit the 3 years old mark.

Funny, it had a 3 year warranty.

The marque had only just been re-introduced into Australia after a good many years. I saw one, fell in love with it and bought it. If I'd waited a few months I would have got it for around half what I paid.

Eau Limpide estate with leather. Horrible depreciation though, cost me $68,000 and I got 22K for it when I sold it They've come a long way since that model.

My first Citroen was a 1220 GS Club which I bought at an auction for 120 quid in England. It died a smoky death on a trip to Edinburgh to see the NZ All Blacks play someone or other in about 1981 or 1982.

I will enjoy Tasmania Citrojim, and thanks!
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Re: C5 Automatic transmission

Post by David290361 »

Brief update:
Vehicle was serviced, new timing belt installed, transmission fluid changed just prior to leaving on our
trip to Tasmania, via South Australia, Victoria and NSW.

12,426 km traveled in just over 3 weeks. Vehicle went flawlessly. Used no oil. Highest temperature we experienced was 48 degrees in the new money near Broken Hill, I don't do Fahrenheit any more!

We cleaned up a bit of wildlife though, 4 rabbits, a feral cat (yay!) and a tree kangaroo.

Going in for a service again tomorrow.
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