Citroen BX autos/ZF Autos: Why do they fail?
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  1. #1
    Moderator Alan S's Avatar
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    Default Citroen BX autos/ZF Autos: Why do they fail?

    Not posting this because I have nothing better to do nor as an ego trip or as a reason to take the 'iss out of anybody, but this week I've had my first opportunity to take a decent look at and become a little educated on the ZF auto in these cars.
    It has always been said that the ZF auto was considered "bomb proof" in the CX yet in the lighter BX it has had all kinds on things said against it; granted not the same box, but rarely does a manufacturer go from a quality product to a crappy one and then persist with the crappy one and it gets used on further models still bearing the crappy reputation.
    I have heard it said on many an occasion that a BX auto "might" last 120,000 klms, so you have to ask, why?
    I'll go back to the start.
    Friend of the family is looking for a car and has a soft spot for my BX. We search high and low looking at cars everywhere but most were neglected, abused or sold, so in desperation I spot a car in Sydney but it's an auto. It has low klms, she's not that happy with an auto but she decides to give it a go, so buys it.
    Happy for a while, but is sceptical of getting anybody to service it near where she lives (with good reason I might ad) and seems nervous about driving it even thiough it only had 80 K klms on it.
    Eventually she brings it up here to me to take for a run and do whatever needs doing to it.
    When I drive it, I'm firstly somewhat impressed at how it gets off the mark; none of the slipping and roaring I am used to with autos. Changes are fair, if anything a bit jumpy in the lower gears but when it goes into 4th, it seems to fall back momentarily in speed, almost as if something is half seizing. This can't be right.
    I check the ATF; it's black. To drain, I find there's two drain plugs both that take an allen key about 5mm. One is set higher in the sump than the other and a look at the ZF manual shows the tp one holds about 1 litre that is splash fed to it. I check the service records and see it had 1 litre of Dexron3 put in it when it was serviced in Sydney prior to her taking delivery. I also note that the insides of the drain plug are partially stripped and vice grips or stilsons have been applied to the lower plug but can't determine if it was removed or not. I remember that Dexron3 came out long after the BX was on the market, so I decide to play it safe and ring a friend who owns a small oil & lubricants company and ask the question as to what it should have in it. He comes back with a different fluid. "Not Dexron3 then" I comment to which he gasps in horror and tells me under no circumstances should Dexron 3 be used in these transmissions. When I ask why, he tells me that the Dexron3 contains additives and extra friction enhancers that makes this fluid incompatable to the set up in these ZF boxes and they should be run on ATF type D2 fluid which is not an expensive ATF.
    Further reading of the ZF manual tells me that the transmission should run at 100 degrees, yet this car had an opened thermostat that only allows the gauge to reach around the 60/65 mark, the original one specifies opening at 82 degrees, so I also replaced that too.
    The result has been, that by removing both drain plugs, I managed to get 2.7 litres of the old ATF out and replaced by the proper stuff and the increase in temp due to replacing the thermostat has the box working at around its optimum operating temp, so now all changes are smooth, there is no drag back on changes and overall the car is much more responsive and pleasant to drive.
    The point is that this car was serviced by a well known repairer who obviously is of the opinion (as I've heard expressed by other repairers in the past) that Dexron3 is the latest of the Dexron fluids and supercedes the others; this is incorrect and according to the iol guy can destroy the internals. Couple this to a box operating below optimum temperature making it think that it's driving the first few miles of the day all day, and little wonder the autos have been blowing up.
    In the past, we have seen on a number of occasions, Dexron 3 being put into C-matics which then causes them to not change cleanly and to also get slow in the synchros and even had some use it in manual gearboxes as they used to back when Total Fluide T was readily available. It is obvious that these guys aren't checking the technical specs before blindly dumping this stuff into them; I wonder how many transmissions these problems and actions have killed?
    Perhaps we had a bomb proof auto all along. It just couldn't stand being poisoned.

    Alan S

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    Last edited by Alan S; 13th July 2005 at 06:37 AM. Reason: More descriptive title.
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  2. #2
    Moderator Alan S's Avatar
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    Due to the responses that came on the "Citroen" Forum and the detail to which this topic was discussed, it has been suggested that it be placed in here as a 'sticky' so as to be more readily accessed by owners in the future.
    Rather than ad another topic, I have decided to attach it as a link to this and as such makes good reading if for no other reason than to give a variety of views and experiences on this (which has turned out to be) most important issue.


    Oil for slugomatic gearboxs


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  3. #3
    Moderator Alan S's Avatar
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    Since this was written, a lot of ATF has passed under the bridge (a different angle on an old saying) and there have been other developments that should interest any BX auto owner.
    To expedite matters, I've stolen these from another forum I posted them on. It again sheds a whole new light on what may have been happening for many years and hopefully will be of assistance to not only owners but genuine repairers as well.
    It could save an owner a car and/or several thousand dollars and as a repairer, should open opportunities for additional service and in so doing increase profits and keep a customer happier for longer.

    This was my initial post:
    A friend of mine has recently bought a BX16Trs auto.
    When he bought it, service records indicated it had been operated on Dexron 3 which we have discovered out here is terminal on BX autos due to its glycol base and not an oil base thereby mixing two incompatable fluids.
    In an attempt to be careful as careful, he bought 20 litres of Dex2 as specified and began a regime of filling and draining in an attempt to get rid of all traces of the Dex3. The difference in the performance of the gearbox has been spectacular until today when he went for a 30 klm trip @ around 120 kph.
    All was going well until someone stopped to do a right hand turn just over a bridge and a tight intersection which caused him to stop. When he tried to take off again; nothing, nowt, ziltch....it just wouldn't move forward. Reverse, yes, but not forward, so he ran it back off the road, stopped the engine and sat there wondering what to do.
    After 5 minutes, he re-started the engine, put into drive and off he went. A few klms further, he again stopped and went to re-start with same result. No forward, has reverse, wait a few minutes and off he goes.
    The theory is that all the crap from teh Dex3 days has been washed out into the system and has got caught in the internal filters as the box can be heard rotating internally when it happens but will not move. If left, all systems seem to go. The theory is that the filters are starving the pump and if left, it drains back down and allows things to work again.
    He's ripping the filters out to clean them so hopefully within 24 hours I'll have a result.
    Does anyone agree with this theory or are we wishful thinking and has anyone here ever stripped a BX auto box and if so, how difficult are they to do work on and where do you get the parts?
    I followed it up with this:
    Well, just had the news; it worked.
    Auto now performing better than it ever did. It seems there's a filter inside the sump of the auto that is like an LHM tank filter and this one was full of shyte. Washed out, it looked like the consistency of half melted chocolate but here's a word to the wise; when/if you take the base plate/sump off the auto, note exactly where the bolts come from. It seems that the service manual donates a full page to this and it is extremely important as if the screws or bolts go into the wrong holes, they actually snag on parts of the transmission and it don't work.
    It also appears on the advice of the guy who pulled the base plate off and in the process studied the whole operation and principle of its operation, that the main problems that befall these transmissions isn't the actual transmission, but is actually the torque converter.
    It seems he now intends ordering a new one for his second car, also a BX Trs auto and doing an autopsy on the current one in there to confirm his theory.
    So it would be interesting to see how many autos have been dumped due to dirty filters, how many have been "reconditioned" by cleaning aforesaid filters and how many have been "fully reconditioned" by simply fitting a new torque converter.


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

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