Auto Transmission Bug in 2002 Citroen V6
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  1. #1
    Tadpole
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    Default Auto Transmission Bug in 2002 Citroen V6

    I'm having an annoying problem with the automatic transmission on my newly acquired 2002 Citroen Exclusive. It has the 3 litre V6 and 4 speed automatic.

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    If I use the sequential shifter all is fine but if I use it in automatic mode it often makes a scraping sound when travelling around 40 kph / 25 mph. If I speed up or slow down it stops. The scraping sound that is.


    Another problem is if I am travelling around 60 kph / 40 mph the engine sounds / feels like it is missing but what I think is really happening is that the transmission cannot make up it's mind as to whether it wants to be in 3rd or 4th and is switching back and forward between the two multiple times per second. When this is happening if I switch to sequential mode and leave it in 4th the engine is smooth as a cucumber.


    Other than these annoyances it's a wonderful car to drive.

  2. #2
    Demannu-facturing! Demannu's Avatar
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    We had exactly the same symptoms in our 406 (same gearbox) just before it died completely. The sound you are hearing is the torque converter lockup function trying to engage but failing. When in the 'sport' program (which automatically engages if you use the manual function), the lockup function is disabled.

    This is a known and common problem with the ZF 4HP20 transmission. If you bought the car cheaply, I would say that someone had already heard the noise....
    Scotty

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  3. #3
    Tadpole
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    Quote Originally Posted by Demannu View Post
    We had exactly the same symptoms in our 406 (same gearbox) just before it died completely. The sound you are hearing is the torque converter lockup function trying to engage but failing. When in the 'sport' program (which automatically engages if you use the manual function), the lockup function is disabled.

    This is a known and common problem with the ZF 4HP20 transmission. If you bought the car cheaply, I would say that someone had already heard the noise....
    Oh. That's sad.
    Last edited by kg2095; 8th February 2016 at 02:34 PM. Reason: Forgot to include quote

  4. #4
    Fellow Frogger!
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    The lock up operates in all modes except snow. Sport mode is not a function of manual shift. Sport mode in auto gives 1000 more revs between gear changes. In manual shift you can bounce the valves [computer willing].

    The jerking is a pressure regulation issue combined with erratically running engine I would say. Most early C5s have this fault and it doesn't affect them. A simple fix, flip it into manual at those erratic speeds if it worries you.

    My thoughts on the noise=Chock the back wheels, jack up both the front wheels and see if you can spin them by hand in neutral. If any drag is felt, check that the handbrake lever at the back of the caliper goes fully forward with the handbrake brake off. Even slight dragging means the traction control will be trying to compensate and hence the noise. If faulty replace the caliper with a non dragging S/H unit. Last price $90. Cheers.

  5. #5
    Tadpole
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    Quote Originally Posted by shanadoo View Post
    The lock up operates in all modes except snow. Sport mode is not a function of manual shift. Sport mode in auto gives 1000 more revs between gear changes. In manual shift you can bounce the valves [computer willing].

    The jerking is a pressure regulation issue combined with erratically running engine I would say. Most early C5s have this fault and it doesn't affect them. A simple fix, flip it into manual at those erratic speeds if it worries you.

    My thoughts on the noise=Chock the back wheels, jack up both the front wheels and see if you can spin them by hand in neutral. If any drag is felt, check that the handbrake lever at the back of the caliper goes fully forward with the handbrake brake off. Even slight dragging means the traction control will be trying to compensate and hence the noise. If faulty replace the caliper with a non dragging S/H unit. Last price $90. Cheers.
    That's what I have been doing - using it in manual mode. It works well this way but Demannu's post has me worried.

    I will give your suggestion about chocking, jacking and spinning a try.

  6. #6
    1000+ Posts George 1/8th's Avatar
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    I'd check that it has new transmission oil, and the correct type and amount. Not under or over filled. The correct spec oil is sold as NULON fully synthetic Transmission oil. Good luck.

    BTW.. mine switches in and out occasionally and I just take it as a feature of that lock clutch. It's no problem.
    Your noise will be something simple.
    2004 C5 V6 Auto, 4 speed. ZF 4HP20.

  7. #7
    Fellow Frogger
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    If the oil pickup is blocked, you may hear noise from the pump, which is close to the bellhousing. It can cavitate and eventually destroy itself. Low pressure can cause a number of behaviour faults and one of them is the converter not lockup up as expected. the manual says it has three states (open, controlled and closed) and the management of these is quite complicated. Anyway, consider two possibilities before condemning the gearbox. 1) Is the transient scraping noise actually a vibration of the gear selector cable against the heatshield under the car; and 2) is the engine vibration due to a failed ignition coil, which is a very common fault and will give you a regular and harsh vibration at about 60, especially with a slight load.

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