Xantia V6 broken exhaust (update: and rough low rpm running)

[NewcastleFalcon]

Simon

I had my own auto transmission tribulations with an Aisin Warner TF-80SC (AF40), box which had only done 60,000 miles on a Vauxhall Vectra. It is fitted to a number of Citroen, Peugeot, Renault, SAAB, Fiat etc models too.

Its documented here AF40 box Knowledge

One link which you may find useful is a video of a method of achieving a full auto transmission oil flush

its American and a Honda but it may be of some use

The key weak point in the AF40 set up on my vintage of Vectra is the standard oil cooler in the radiator.

One of the contributors to my thread wrote

"Vectra auto box oil coolers have a tendency to rot the seals built into the radiator, thus letting coolant into the oil, destroys boxes in no time. Drain a little oil onto a spoon and hold over a flame, anti freeze in the oil will show up when it starts boiling and spitting whereas oil will just smoke. Hope this is some help to you "

Maybe the cooler and contamination of the oil may be at the root of your problems too.

I am no expert but I think I would take up Jim's offer. The changing of the fluid no doubt helps, and a full flush out even better. With careful driving I got 20,000 additional miles out of mine before the inevitable rebuild was necessary.

kind regards

Neil

[lexi]

Your Aisin experiences are interesting. I put that failure down to poor components used by Vauxhall rather than box itself.
There are few failures on Vel Sat Aisin boxes and obviously the implementation and component layout is different.

Old Patrols with Jatco auto boxes suffered the water contamination eventually..........after about 15 years and 300k
All slightly OT but it is Auto box talk

[Mandrake]

Paul, I quite agree - go for it Simon! What have you to loose...

I'm quite surprised to see you behind the idea Jim, with your (very reasonable) obsession that nothing other than LT 71141 should go into a 4HP20.

Is it just that we've reached the "nothing left to lose" point, or do you think ~250mL of a (seemingly) well regarded additive added to the correct original oil is a different matter than just putting the wrong oil in completely, and far less likely to do harm ?

In my searching I can find very little negative about the Lubegard ATF products especially Lubegard Red which is the one Paul is suggesting. At worst I've seen a few "it didn't help" comments (probably from people expecting miracles on a box that is well and truly guffed) but an awful lot of positive feedback particularly regarding improving clutch shudder and shifting quality.

There seem to be a few aspects to the claimed function of it - helping to free up sticking valves in the valve body, improving the low speed frictional characteristics of the oil to prevent clutch shuddering, improving heat transfer / heat sinking ability of the oil to lower operating temperatures a few degrees, and reduction in oxidation of the oil at high temperatures to help prevent burning of the oil.

I'm a bit unsure about exactly which one I should be trying though, as their spec sheets don't specifically list the 4HP20 nor Citroen - not surprising when the spec sheet is for the US market where PSA cars are a no-show.

These are the different ones here:

http://www.lubegard.com/C-110/Transmission" onclick="window.open(this.href);return false;

And here is the "conversion and refill" chart:

http://www.lubegard.com/pdfs/2010_LUBEGARD_CC_FINAL.pdf" onclick="window.open(this.href);return false;

It's a little bit confusing but it appears that Option 1 is for when you are only adding an additive ("protectant") to the original oil type, while Option 2 is is when you are using a "supplement" to convert Dexron III into an equivalent of one of the other oil specs. (I'm assuming the "suppliment" version has an additional friction modifier pack etc)

Looking through the columns there are plenty of gearboxes listed with LT 71141 including the 5HP24 which is confirmed by other sources to use LT 71141 and it says if you're using original oil to use either Lubegard Red or Lubegard Platinum.

Here's where it starts to get a bit hairy. In the option 2 column for the 5HP24 (under Audi A6) it also says you can use Lubegard Platinum (but not red) with Dexron III, VI, or Mercon, the implication being that Lubegard Platinum has whatever components are missing in Dexron III et al to bring it up to spec for LT 71141. I'm assuming the differences are friction modifiers although they don't really say clearly.

If that's the case, why is it ok to use Lubegard Platinum with the original oil as well ? Wouldn't we get a double dose of whatever those additives are ?

Other puzzling points are that the 4HP18 (which I thought used Dexron II) is listed in a number of places for different models of car, but the "original" oil (option 1) is listed as different oil for different cars -

For example for the 4HP18 in a Saab9000 they list Dexron III as the original oil, but the 4HP18 in an Audi 100 lists LT 71141 as the original oil! Is it possible that the same model of gearbox in two different brands of car could have shipped with completely different types of oil, and if so what is so different about the oil ? A bit confused...

It has to be either Red or Platinum but I'm leaning towards the Red version which seems to be a basic one without additives that try to convert the oil from one type to another. If you look in the Platinum section it says things like:

"Enhances DEXRON® III, VI/MERCON® , V ATF to perform like a highly friction modified ATF, such as:
– Honda® Genuine ATF
– Toyota® Type T/TII/TIV
– Mopar® ATF + 3® (7176)
– Mopar® ATF +4® (9602)
– And all other highly friction modified ATF's"

However I can't seem to find anywhere whether LT 71141 is a "highly friction modified" oil or not. One source that I did find said that LT 71141 was basically Dexron IID spec (in terms of viscosity with temperature etc) but with different friction modifiers, but it wasn't a reliable source. Does highly friction modified mean more friction (clutches grip more strongly under load) or less friction ? If LT 71141 is indeed a highly friction modified oil and Dexron III is not, does that mean the use of unaltered Dexron III in a 4HP20 would cause the clutches to slip under load thus wear out the box rapidly ?

I suppose I could always contact the company and see what they say about which one to use...

Edit: their FAQ has this to say:

What’s the difference between the four colored bottles?

LUBEGARD ATF Protectant (red) - Is for use in any recommended ATF by the manufacturer. LUBEGARD Platinum Universal ATF Protectant (platinum/silver) Eliminates all ATF confusion. - Use as a universal ATF conversion supplement. - or use as a ATF Protectant with any OEM recommended ATF. LUBEGARD Highly Friction Modified ATF Supplement (black) - Is for use to convert DEXRON III, VI/MERCON, V into a highly friction modified type of ATF. LUBEGARD M-V ATF Supplement (green) - Is for use to enhance DEXRON III, VI/MERCON into a MERCON V ATF.

Does the LUBEGARD Platinum product replace all the other ATF products (red, black & green)?

Yes

Should I use the LUBEGARD Platinum instead of the other products?

We suggest Lubegard ATF Protectant when you are using the recommended OEM ATF’s. However if your vehicle has a shudder present we do suggest using Lubegard Platinum. LUBEGARD ATF Protectant also eliminates shudder but Platinum’s Synergol Technology provides more wear & friction benefits.

Have to say I'm a bit dubious about the ability of the "Universal" (platinum) version to work both as a modifier and with original types, but that's what they say...

[Mandrake]

The key weak point in the AF40 set up on my vintage of Vectra is the standard oil cooler in the radiator.

One of the contributors to my thread wrote

"Vectra auto box oil coolers have a tendency to rot the seals built into the radiator, thus letting coolant into the oil, destroys boxes in no time. Drain a little oil onto a spoon and hold over a flame, anti freeze in the oil will show up when it starts boiling and spitting whereas oil will just smoke. Hope this is some help to you "

Maybe the cooler and contamination of the oil may be at the root of your problems too.

Thanks Neil,

Coolant contamination is something we've considered and checked earlier in the thread, but not conclusively ruled out.

In the oil that I've drained at 80 degrees there is definitely a tiny bit of moisture in it when looking at the samples I still have in glass test tubes, while the one drain that I did when the oil was over 100 degrees has no condensation in it at all - presumably the water will have steamed out at that temperature during the draining.

As far as I know its just condensation and no traces of coolant colour were found, HOWEVER having said that I've been running with the pressure cap loose for many months now due to coolant loss with the cap tight. I definitely have a split in the coolant expansion bottle that leaks under pressure (I loose no coolant at all with the cap loose) however that is not to say that there isn't a pinhole in the heat exchanger that lets some coolant through to the oil but only when the coolant is under pressure.

If that's the case my running with an unpressurised coolant system for all these months may have helped it to last as long as it has. I guess the only way to really know would be to disconnect the heat exchanger and do a pressure test on the coolant side to see if anything comes out the oil side ?

The idea of putting some of the drained oil in a spoon and heating it to see if it sputters is a great one, I will try that when I do the next oil change possibly this weekend, only thing is I'm not sure how to distinguish a small amount of condensation from actual coolant in that test.

[DHallworth]

Simon,

Mackie's transmissions in Glasgow do the hot flush with the proper machine. They charged a friend of mine £150 to do one for his Range Rover using the LT71141 and it takes around 8 litres of it from memory so I'd expect them to charge a bit less for a 4HP20 flush. The difference in the way his gearbox drove afterwards was incredible!

Even though my XM has only done 50k I'm sorely tempted to book it in for a hot flush and then I know it's got good oil in the box.

David.

[larppaxyz]

Thanks for taking the time to read and respond to my thread! Its reassuring that I'm not the only one who has experienced this odd array of symptoms! Perhaps if we compare notes we might be able to pin down the cause.
You'll find the torque and power curves for the ES9J4 here:
http://club-xm.com/forum/index.php?showtopic=2873&st=0" onclick="window.open(this.href);return false;

This issue is very common with ES9J4, you can find some information from Peugeot forums too. I do have torque curve for engine that runs well, but there was torque curve for engine that had this same issue. Issue was very visible on curve, huge flatspot on low rpm (around 1500) until it hits 4000rpm.

Yes this is exactly what I experienced when the engine was running at its worst a number of months ago - p**s poor power low down but upon reaching 4000 rpm it would instantly zoom away like a scalded cat. Always at the exact same RPM, and as you say the exhaust note changed too.

ECU goes to open-loop mode at 4000rpm. It ignores some sensors and uses precalculated values for maximum performance. This information can be found from Bosch ECU manual (you can google it up for our ECU model). Manual has some very interesting and detailed information.

Have you fitted new spark plug leads to the rear bank, and new spark plugs all round ? What type of spark plug are you using ? I'm now using Bosch FR8KDC and they are working better for me than either of the previous two types.

I havent changes plugs for long time, i can't remember what they are. Leads are original and 'look' fine. But there could be some oil in rear bank. I haven't had time to check that.

Yes I've had this as well - a few pages ago you'll see a video I recorded of the RPM going +/- 200 rpm when trying to hold it steady at 1500 rpm. At the time I correlated it with the torque reduction ignition retard figure, which was going to 15 degrees of retard each time the rpm dropped, and back to zero as it rose again, although I don't know what was causing it.

As for "bad idle" do you mean that when you come to a stop (or sometimes when starting a hot engine) the revs will drop to try to stall, then surge up, then drop to try to stall, sometimes up to 3-4 times ? Mine has done that intermittently for a long time, and I can't find the cause of that either.

Yes, by bad idle i mean those 'almost stalling' issues and RPM going +/- 200 rpm on steady gas and low rpm. This is the main issue i'm having, when there is no idle issues, low RPM power is back too.

Are you sure your torque converter is not having problems ? Have you ever heard it make a "groaning / grinding" noise under load at 1500rpm ? Have you done any oil changes on the gearbox ?

I have done two oil changes, they made no difference. Gearbox works very well overall, no error codes, no stuttering... there is this idiotic 2nd -> 1st gear change when stopping to red lights. This also disappears when idle issue is gone.

Switching to neutral doesn't make any change to idle or how engine runs.

I think my gearbox is fine, on other forums some guy swapped his gearbox and issues remained the same. There has been some talk about engine speed sensor controller box located unders glovebox (on peugeot). That has some affect to power steering and gear change issues... i cutted my controller box open and i just could not see any components that could fail (there was no condensators or such components).

It's pin 51 on the gearbox ECU which goes to pin 42 on the engine ECU.

I would not advise cutting it as it would put additional strain on the gearbox clutches, at the least the gear changes are likely to be rough, at worst it could damage the clutches if the gearbox is old and worn out. I plan to connect a small digital oscilloscope to that control line on mine so I can monitor WHEN the gearbox is commanding torque reduction to rule out the gearbox as the issue.

I don't have oscilloscope so testing it with cut wire would be my only option. I would love to hear what your oscilloscope shows . In theory you could make gear changes faster by manipulating this signal.. but thats different story (you could use Arduino and few lines of code to do this).

Do you know where the earth points are for the engine and gearbox ?

One thing that occurs to me as well is the knock sensor has a special cable with extra shielding as its in a very "hostile" position yet produces a very low voltage high impedance signal, I wonder what the effect of a broken shield would be on the knock sensor cable ? It may be intermittently picking up interference from the ignition and other devices triggering erroneous knock related timing retard.

I think i should check knock sensor on my engine. I think main earth point is under battery box, but i need to check that. There usually is bigger earth lead going to engine block and that could be loose after all these years warming up and vibrating.

In most cases where my engine has felt down on power it has felt like retarded timing. Although its running much better lately, once again today after a lot of driving the low rpm performance has sagged quite noticeably, feeling a bit "lethargic" and unresponsive at low rpm, but after sitting and cooling for a couple of hours the performance is better again. It usually seems to be worst when warmed up.

Sound very very familiar. Somehow engine/gearbox temperature affects this issue. And i know it's not running too hot because i have had this issue on winter -30C degress

I definitely need to bleed the cooling system, although when I have monitored the coolant temperature via a Lexia I have never seen any evidence of the sensor reading incorrectly or erratically.

My diagnostics also show me that temperatures are fine, but bleeding should be done anyway. This thing however should not have anything to do with idling problems. However gearbox is cooled with cooling water also, am i right...? Water circles in heat exchanger on top of gearbox.

Edit: one other thing that may be worth checking is the quality of the signal from the crank shaft sensor. Now that I have a small digital scope I might try to get a reading on this on the back of the ECU plug if I can get the cover off the plug. The only problem is we're moving house at the moment (twice!) so it could be a month or more before I get a chance to do any further testing on the car.

Do that please, i have had two cars that needed crank shaft sensor replacement.

Oh, and i use 98 octane fuel, those octane ratings are probably bit different here at Finland, but it's pretty much best you can get and only has 5% ethanol.

[Mandrake]

ECU goes to open-loop mode at 4000rpm. It ignores some sensors and uses precalculated values for maximum performance. This information can be found from Bosch ECU manual (you can google it up for our ECU model). Manual has some very interesting and detailed information.

Aha, I thought the ECU might be ignoring some sensor inputs above 4000rpm. I read somewhere but can't confirm that the knock sensor signal is ignored above 4000rpm but perhaps there is more to it than that. I don't suppose you have a link to the MP7.0 technical manual ? I would be very interested in getting a copy. Send me a PM if you prefer not to post it in public.

I havent changes plugs for long time, i can't remember what they are. Leads are original and 'look' fine. But there could be some oil in rear bank. I haven't had time to check that.

My plug leads looked fine visually too however two of the three leads when tested were internally broken at the sharp bend where the wires from the rear cassette curve around to the back of the inlet manifold. When the wires were bent in a certain direction they measured normal (about 6k ohm) but when bent another way they were open circuit. I believe that they were going intermittently open circuit with vibration and temperature changes causing intermittent problems with the spark.

I believe this was a good part of my low RPM power loss - a lower spark voltage due to broken leads (the spark will still jump inside the lead to reach the plug but the voltage will drop) can lead to a misfire at high combustion pressures which are at a maximum at wide throttle at low rpm. This means that the spark will be sufficient at idle with a closed throttle or at high RPM and low to mid throttle, however at lower RPM and wider throttle there will be a misfire.

Because its a wasted spark system with pairs of spark plugs connected in series a low voltage misfire can affect a pair of cylinders for example one faulty plug lead causing a misfire on both cylinder 1 and 5 which share the same coil. Because the two misfires are evenly distributed in the engine timing cycle the engine will not rock and vibrate as much as a single cylinder misfire (but will feel rough) so it won't feel as much like a misfire, but there will be a huge loss in power from two non-functioning cylinders.

The un-burnt oxygen from the misfiring cylinders will also cause the oxygen sensor to read lean causing the ECU to incorrectly try to richen the mixture and retard the timing causing further power loss. If your plug leads are original and you have been chasing this low RPM performance issue for a long time I would highly recommend you change the plug leads (new ones are around £40 if you look hard) and also the plugs, and stick to the original type Bosch FR8KDC not an equivalent. If nothing else it would help you to eliminate two possible causes of trouble!

A test that you could perform is to look at the oxygen sensor voltage on the Lexia under wide open throttle at low rpm (1500-2500) while in a high gear driving up a hill. (Try 3rd in snow mode to lock it in 3rd gear) You should see a constant rich reading (voltage over 0.8v) even at full throttle but when mine was misfiring due to the plug leads I was seeing a lean reading (voltage under 0.2v) under wide open throttle below 2500 rpm which then changed to a rich reading above about 3000 rpm. I believe this was a misfire causing un-burnt oxygen to pass through to the oxygen sensor, at higher rpm the misfire went away and the oxygen reading returned to normal. I no longer have this problem on mine.

I've also replaced the oxygen sensor, which was very slow responding. I believe my oxygen sensor was the original factory one as it had a manufacturing date of 1998. Has your oxygen sensor been replaced ? The oxygen sensor speed is difficult to test on a Lexia as the numbers do not update quickly enough, I tested mine using an oscilloscope. It's not enough to see that it switches high and low, it needs to switch at least twice per second at 2000 rpm which is difficult to see on a Lexia.

Yes, by bad idle i mean those 'almost stalling' issues and RPM going +/- 200 rpm on steady gas and low rpm. This is the main issue i'm having, when there is no idle issues, low RPM power is back too.

Mine is still intermittently doing the "almost stalling", and the +/- 200 rpm fluctuation at 1200rpm, however not very often, and it seems to be temperature related. Can you check the ignition timing data on your Lexia while the RPM goes up and down 200 rpm with a constant throttle ? I bet you will find the torque reduction retard figure is jumping between 0 and 15 degrees every time the speed varies...

I don't have oscilloscope so testing it with cut wire would be my only option. I would love to hear what your oscilloscope shows . In theory you could make gear changes faster by manipulating this signal.. but thats different story (you could use Arduino and few lines of code to do this).

As soon as a I get a chance to test this I'll post the results in this thread.

I think i should check knock sensor on my engine. I think main earth point is under battery box, but i need to check that. There usually is bigger earth lead going to engine block and that could be loose after all these years warming up and vibrating.

The knock sensor is hard to test - the Lexia does not provide any data on the knock reading unlike OBD-II engines, and there is no bias voltage on the sensor either like most later cars. The only way to test it would be to use an oscilloscope, again I plan to try to connect my oscilloscope to the knock signal to see what is happening.

My diagnostics also show me that temperatures are fine, but bleeding should be done anyway. This thing however should not have anything to do with idling problems. However gearbox is cooled with cooling water also, am i right...? Water circles in heat exchanger on top of gearbox.

Yes there is a heat exchanger to the engine coolant.

Do that please, i have had two cars that needed crank shaft sensor replacement.

Yes I also plan to test this signal with my 'scope So that's crank sensor signal, knock sensor signal, and timing / torque reduction signal that I will try to test. It could be a while before I get a chance to do it though.

[CitroJim]

Paul, I quite agree - go for it Simon! What have you to loose...

I'm quite surprised to see you behind the idea Jim, with your (very reasonable) obsession that nothing other than LT 71141 should go into a 4HP20.

To be honest Simon, I think at this stage you have little or nothing to loose and potentially a bit to gain..

In normal circumstances I'd be absolutely dead against it but you know I've used snake oil in the past on things that are on the edge anyway to keep them going just a bit longer. Wynns in the knocking Volvo 340 for instance...

[Mandrake]

Fair enough Jim. I've convinced myself that I will try the Lubegard, a lot of people are saying many transmission overhaulers put it in as a matter of course after a rebuild, it can't be too harmful or just snake oil if that's true!

Its just a matter of choosing the Red or Platinum, and it may come down to a coin toss

Both are recommended, however the "Red" formulation is the original one that has been out for many years and is the more "conservative" one to use as it doesn't contain any friction modifiers in it, and therefore is designed only for use with original spec oil.

The platinum "universal" one has all the same components as the Red but in addition it has a modest dose of friction modifiers in it as well as an additional surface anti-wear agent not found in the Red.

From the research I've done clutch shudder, torque converter in particular occurs when the static friction of the clutch is greater than the dynamic friction, which makes it "grabby", making it impossible for the ECU to regulate a small (50-100rpm) controlled slip in a smooth fashion, the shudder coming from the clutch grabbing and releasing as the ECU tries to regulate the slip.

For a normal dry metal to metal contact surface (or indeed most solid surfaces rubbing on each other) static friction is always greater than dynamic friction. The "friction modifiers" that are in the ATF are there solely to change the friction curve to reverse this trend so that friction remains relatively constant as slip reduces but then decreases instead of increasing just as the clutch locks up, causing a smooth transition.

It seems that one of the major differences between different ATF's is the amount of friction modifiers in them, (and therefore the shape of the friction curve) with LT 71141 possibly having higher than typical amounts of friction modifiers in it, and higher than Dexron III.

As the oil wears out, thins and oxidises, and contaminants build up, the friction modifiers loose their effectiveness and when you reach a point where the static friction is significantly higher than dynamic friction shudder starts to occur.

Although they say that the Red version will help somewhat with Shudder, they recommend the use of Platinum if there is significant clutch shudder, even with original spec oil, I'm assuming the reason is that the extra dose of friction modifiers introduced into the oil helps revert the friction curve of the old oil back to closer to what it should have been without replacing the entire 8 litres of oil...(perhaps something to only be done once, and then use Red with subsequent oil changes)

So if I want to play it safe but maybe not get maximum results I use Red. If I want to play a bit fast and loose but with more to gain if it pays off, I choose Platinum... oh the agony of choice...

I will be doing a standard oil change on it this weekend anyway, it will be the first time in over 6 months so it will help me to evaluate the state of the oil compared to the last change.

In 2 or 3 weeks I'll do a second oil change and put the additive in then. So I won't just be putting additive in, there will be two oil changes as well. I figure that the cleaner the oil is to begin with the better its chances of working and giving a more long term result. I don't expect miracles in dirty oil!

[Mandrake]

Well I did a gearbox oil change over the last couple of days, interrupted only by this small crisis where I discovered that the Banjo was leaking oil:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=44683" onclick="window.open(this.href);return false;

It's been 6 months and about 2000 miles since the last oil change I did in a series of four oil changes to try to "resurrect" a seemingly about to die box, and I'm pleased to report that the condition and colour of the oil was almost identical to the last change - I was going to take a new photo of the 5 specimens side by side in their glass test tubes but there really is no visible difference between the last two changes. The oil could be cleaner but there has been no visible burning of the oil in the last 6 months.

In the last month leading up to this change the gearbox has been getting a bit cranky, the most obvious symptom was torque converter lockup clutch shudder when pulling under load at low rpm in 2rd and 3rd with the clutch engaged, it was getting to the point again where I was manually downshifting when crawling up a 25mph incline behind slow traffic rather than let it struggle...which is how it was behaving last year before the series of oil changes.

I'm pleased to report that the shudder whilst not entirely gone has gone from quite objectionable to just barely noticeable. In most instances it will pull up a slow incline in a high gear without any shudder now, not so a few days ago. So despite the oil coming out looking no dirtier than the last lot 6 months ago there is clearly something changing between old and new oil, which gives me some hope.

After the reading I've been doing about Lubegard etc, I believe that what's happening is that the quantity of friction modifiers in the oil is still marginal despite all the oil changes I've done, because the original oil was so extremely dirty and worn out (the friction modifiers deteriorate and lose effectiveness over time) and I can never entirely replace the oil without a hot flush only dilute it, making it difficult to restore the correct strength of friction modifiers with normal oil changes without an excessive number of changes. (diminishing returns with each change)

The oil change I've just done will have (apart from resulting in cleaner oil) injected some fresh friction modifiers into the mix, and I believe this is what has stopped the shudder, however I suspect that it will still be marginal and may start shuddering again in a few months if I don't do anything else.

Because of this I think I'm going to go with the Lubegard Platinum rather than the Red, as it includes a dose of friction modifiers as well as the other lubricating properties and should give the existing oil a "shot in the arm" in terms of boosting the quantity and strength of friction modifiers and have a longer lasting effect, as well as making shifts a bit smoother.

Other symptoms that the gearbox has intermittently had in the last month or so is the occasional "slip-bang" change from 2nd into 1st, where you're slowing down for a junction in 2nd then accelerate hard just before stopping, on occasions it will slip with no drive for a fraction of a second then bang quite harshly into 1st. It's been doing it often enough to make me wary of planting my foot at a roundabout until I'm sure it has finished engaging 1st gear. Upshifts have been a bit more abrupt lately as well and not as smooth as in the past.

I'm highly suspicious of slow/sticking valves in the valve block, because as well as the above symptoms I think that a lot of the intermittent performance issues I've been chasing recently are in fact the torque converter lock up clutch being slow to respond to the ECU commands, perhaps not responding at all sometimes due to valve block mis-functioning.

I'm very sensitised now to the operation of the torque converter clutch after studying it in such detail, I can hear and feel when it engages, and I can say that it definitely does not behave consistently, and that in the majority of cases where I feel that the performance is sagging when it shouldn't be, the TCC lockup is also behaving "oddly".

My gut feeling is that because the symptoms are so intermittent that its not likely to be the clutch linings being worn out that's causing it, (or it would be bad all the time) but rather a control issue like sticking valves or low pressure. If I put it in 3rd snow above 2500rpm it will lock the clutch and I can floor the accelerator (nearly 260Nm) and the clutch will not slip, if the linings were worn out it would slip in this scenario.

After Sundays oil change and banjo pipe repair I took it for a few test drives checking various things and apart from noticing the clutch shudder was almost gone I noticed that the performance seemed MUCH better, and more importantly more responsive and direct especially in sport mode. Not all the time, sometimes it was still a bit funny but the peak performance was definitely a lot better than it has been for a while now, so I'm convinced that the remaining intermittent performance issues I've noticed may be largely gearbox related, more specifically the TC lockup clutch not doing as it should, when it should, reliably. (If the TC clutch is slipping when it should be locked acceleration will feel "mushy", when its locked it gives a very direct almost manual gearbox like sharpness to acceleration)

Symptoms that didn't go away with the oil change are the slightly abrupt upshifts and the intermittent "slip-bang" change from 2nd to 1st when accelerating while slowing, I tried an auto-adaptive reset but it didn't really seem to help.

Both of the Red and Platinum Lubegard additives say that they are good at helping with unsticking the valve block so I think its definitely worth a try as sticking valves could be a major contributor. They also have a gearbox flush product which I'm considering using as well:

http://www.lubegard.com/~/C-178/LUBEGAR ... sion+Flush" onclick="window.open(this.href);return false;

You put it in before you drain, run the engine for about 5 minutes in various gears with the wheels free to turn then drain the sump and do a normal oil change, (optionally with the Red or Platinum added) so I'm likely to use that as well.

What do I have to lose ? I'm willing to take an arrow in the back for the forum to see if these additives live up to their claims in dodgy gearboxes!

[Hell Razor5543]

The only problem I can see with the gearbox flush is that (unlike a BE3 or ML5T manual 'box) half of it will remain in your gearbox when you drain it. I would contact Lubegard first, explain the situation, and ask for their opinion.

[Mandrake]

Fair comment, I've looked into that already though, in their FAQ they state that its ok to just do a sump drain after using the flushing agent, as there's nothing in it that would be harmful in the long term. The product is formulated with a partial drain in mind since all (?) autos don't allow the torque converter to be drained via the sump.

The flushing agent also has the LXE components that the Red additive has so I think when you read between the lines it looks like the formulation of the flushing agent is similar to the Red additive but most likely in quite different proportions with a much greater percentage of detergents.

[Hell Razor5543]

I would still ask them directly, and if they are not certain I would not use it. It would be a shame to kill the 'box after all you have been through with it. If they say it is safe to use it, ask them nicely if you could get that in writing. That may already be on their packaging. The problem is (obviously) the oil in the TC. I wonder how many auto gearboxes fully drain down?

[sandybx]

Dear Mandrake,
I have an automatic BX that runs Dextron 2 automatic transmission fluid and I was reading someones thread about automatic transmissions fluids, and he was saying that Dextron 3 is totally uncompatable to be used in an automatic gearbox that is designed to have Dexton 2. He was also saying that Dextron 3 has some kind of built-in antifreeze added to it.
I didn,t know how true his statement was, but I was wondering if you have heard the same ?
Vince,

[lexi]

I know another type of oil that is going to be dirty,.........that engine oil is in there over 13 months