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Discussion Starter · #1 ·
Hello All, I have done a lot of research and read all of the posts on suspect torque converter problems. I have been thinking about this a lot and I thought it would be a good idea to get some feedback from this community. I realize many of you have had problems with fluctuating RPM’s at certain speeds, shift problems, cattle grid noises, grinding etc… According to the hundreds of threads I have filtered through on this board and a few other Land Rover boards the fix has been to swap out your torque converter which resulted in curing “some” of the issue but not “all”, particularly the RPM fluctuations between 30-50 mph. According to many threads on this board as well as other sites, it seems there are many of us who have no shifting issues, no cattle grid noises yet we have that annoying throttle fluctuation in "D" between 30-50 and the vehicle seems to always want to shift to a higher gear 4,5th going up hill even at low speeds which seems to make the RPM fluctuations worse and the remedy is to press on the gas pedal and get the vehicle to downshift to a lower gear or move the shifter to sport mode.

We might be talking about 2 separate issues here with different cures. I know that the symptoms do not typically occur in sport or manual mode. That leads me to believe that in some cases the problem might be how the computer reacts to the normal wear or degredation of the torque converter. In other words the torque converter might very well be worn/old but has it completely failed and need to be replaced? Since the ECU is hard coded maybe it doesn't know how to respond to a worn torque converter and disengage the slip mode appropriately or completely where necessary..(low speeds, uphill etc).. I hope I am making sense here. I have yet to see one sure footed fix for the RPM fluctuations. Can the ECM be reprogrammed to disable slip mode in "D" so the torque converter slip mode is not speed sensitive? Thanks for reading and I appreciate your collective input..
 

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I agree...

I took this video of my car after TC replacement, I think this is the slip function at work.. it´s more or less pronanuced during different scenarios. I just got my IID tool with a special firmware that allows me to track the clutch and solenoids. I´ll be revisiting this issue in more detail later.

 

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Clearly diagnostics is the way to go i.e. monitoring & recording what’s going on in real time so that you can analyse these events properly. Problem is, the kit only tells you when the solenoids are being activated by the ECU (and at what level/current) but not their response. For that you’d need to start measuring pressures as well. The engine, turbine and output shaft speed signals are useful but the issue I had with the Faultmate was that the values are only captured at 1Hz and one second is a long time when you’re looking at gearshifts, vibrations, etc.











Phil
 

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iidtool is supposed to be able to sample one value at 8hz, two at 4hz.

So I guess one have to do a couple of runs with each.
 

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Discussion Starter · #5 ·
Thanks for your replies and providing the graphs. Is the slip mode controlled by a solenoid inside the transmission that gets the signal from the computer? If so, can the selenoid be sending the wrong signal or be defective? Also is it the engine computer that sends the signal to the torque converter to go into slip mode or the transmission computer?
 

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This information is for the ZF 5HP24 transmission fitted to ’02-’05MY 4.4 litre V8 models with the BMW petrol engine:

Yes, an individual solenoid (driven by the transmission ECU) is responsible for the operation of the torque converter lock-up clutch. It’s usually identified as EDS 4. The three other black-capped solenoids (labelled A, B & C in the photo) are all identical to the LUC solenoid so you could swap them about if you wanted to try to trace the fault through substitution. There is a small risk of upsetting the long-term controller adaptions but I personally don’t see this as significant.



Phil
 

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Discussion Starter · #7 ·
This is very interesting and informative. Phil, in your experience have you come across any failures of these solenoids? Does the whole harness need to be changed or are the solenoids individual parts? That wiring harness and those solenoids soak in Trans fluid in the pan all day every day, is that right? Could one the solenoids or wires fail or corrode and not throw any codes giving the owner the impression that everything is working as it should? if so what would be the symptoms? What if the "slip mode" solenoid or one of the others isn't working properly or receiving bad signals? Could a failed solenoid cause the vehicle to go into slip mode prematurely or when not necessary? For example; Slip mode or upshift engages at the wrong time, going up hills or in slow and go traffic, when down shift is actually needed to get up the hill or maintain speed to the flow of traffic etc...Its the slip mode that causes my vehicle to have the RPM fluctuations, once i get over 50mph and over 2k RPM which ever comes first, she is fine. Also in sport mode where the slip mode is "bypassed" it seems to run just fine through the gears and maintain a lower gear up hills and in traffic. When in "D" At low speeds my vehicle wants to upshift to 4th or 5th gear for some reason could that also be a malfunction of a solenoid on that harness? Thanks for your help and sharing your technical knowledge, please help keep this thread going..
 

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Phil, how would you feel about disabling the partial lockup altogether? Seems like that'd solve quite a few issues...
 

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The lock-up clutch solenoid (EDS 4) is one of a total of eight used in the valve block, all of which can be replaced separately and purchased individually.

The ‘off’ condition for the solenoid results in the LUC being disengaged and then applying current increases the hydraulic pressure behind the LUC piston to engage it i.e. in the event of a transmission electrical failure the limp home condition is an open converter.

In theory you could therefore disable the lock-up clutch by just pulling off the EDS 4 electrical connector. However the transmission ECU monitors each solenoid for open and short circuits to battery or ground. I guess you could try kidding the ECU by placing a 6.5 Ohm resistor across the disconnected terminals though I suspect that the ECU will check the difference between the engine (impeller) speed and the turbine speed when it believes the LUC is fully applied and then flag a fault when the speeds from the sensors aren’t identical, or that it isn’t managing to maintain a 3% slip speed when the LUC is partially applied between 25mph and 56mph. The only realistic bypass I can see would therefore involve rewriting the control code.

Replacing the LUC means replacing the complete torque converter which is a ‘transmission out’ job (5 hours labour) but it is not necessary to open up the transmission so any competent mechanic can do this without any specialist transmission knowledge. However, a point I would make is that the lock-up clutch in the Sachs WA4/W260 S-2GWK unit used in the 5HP24 is quite difficult to re-manufacture.


LUC piston in green, friction plate in red


LUC friction plate

The total piston movement, on to off, is only 1mm and the retainer for the piston return springs - which double as tangential driving straps - is friction welded into place so has to be turned off on a lathe and then accurately re-welded in the correct position once the friction plate has been replaced.



For that reason torque converter remanufacturers shy away from this particular model or, if they do offer to recondition it, may not risk attempting to replace the LUC. I’d strongly recommend that anyone sourcing a replacement torque converter should find somewhere that has a lot of experience with this particular model (e.g. JPAT or Sussex Auto Parts, if you’re in the UK)

Phil
 

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Hey Phil, I mean turn it off via software (as you say, re-writing the control code). Maintain the normal full lockup, maybe even change the minimum speed/gear at which it occurs, but disable the variable slip. No fault codes, no warnings. Just change the conditions under which it is active so that it's never applied.

I'm sure fuel economy would decrease a bit, but in my experience we're not talking about astronomical differences.
 

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Discussion Starter · #11 ·
Can the LUC solenoid or any of those solenoids fail or not work properly? If so, I assume if they weren't working as the should yet not completely failed they wouldn't throw any codes, they would just not function correctly, is that right? Take a look at Shogo's post above, changed his torque converter but still has the RPM fluctuation while in the "slip mode band". I wonder in that case if LUC solenoid or the wiring harness was the culprit vs a failing torque converter? Is it a good idea to change/check the solenoids and wiring harness first before swapping the converter? Thanks for the follow up.

DDiilenger, it might be very difficult or near impossible to reprogram the ECU, but a great suggestion. I look forward to seeing Phils response or other Pro's that might want to weigh in on this.
 

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I tune the bosch EGS regularly in other applications. I have no doubt I could do it given enough time. My comments weren't directed at your situation, more of a side conversation :)
 

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Discussion Starter · #13 ·
Not at all. I appreciate your input. I did not realize reprogramming might be an option but that would be fantastic, decreased mpg wouldnt bother me all that much If can get the variable slip fixed via software vs hardware.
 

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@ ddillenger : it’s very interesting to hear that you have the capability to reprogram the Bosch controller (I wouldn’t have the first idea where to start). Clearly this opens up all sorts of possibilities. I think the only downsides of switching off the LUC operation are, as you say, the hit in fuel economy and also a slightly higher heat load going into the transmission fluid. If you can just ‘remove’ the continuous slip mode while still maintaining full lock-up above 56mph though, I would imagine these disadvantages aren’t going to be significant

@ NRL1029 : the solenoid swap is relatively straight-forward (if you don’t mind oil dripping on your head) so you could try this first. I have loads of the solenoids lying around if you need a spare (though obviously using an untested second-hand one isn’t without its own risks)



Without the necessary flow/pressure test kit the only thing you can check for the solenoid and its wiring is the winding resistance (which, as previously mentioned, should be around 6.5 Ohms) between pins 11 & 16 at the rear connector. This clearly doesn’t give you much idea whether it is functioning correctly, though.



Another possibility, of course, is wear in the valve block itself. There are two spools and a single damper which control the torque converter hydraulics and these live in the lower front valve block :



The only reliable way that I’ve found of determining valve block (spool & bore) wear is by vacuum testing :



Phil
 

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Discussion Starter · #15 ·
Great information, thanks for taking the time to post and the illustrations. I think the next time I head over to my LR Indy shop for transmission service I am going to have them change the wiring harness and LUC solenoid to start. I don't want to change the torque converter just yet and still have the "continuous slip mode issue" unless I really have to, so I will start with the harness and the solenoid. They've been soaking in trans fluid for 11+ years so maybe a refresh would help, unless you guys think that is not a good idea for some reason let me know. This is not something I could do in my driveway. Altantic British has the wiring harness in stock but I do not think they sell the solenoids. Can someone provide part number or where I can buy them?

Thanks again all. It's great that we can communicate like this across the globe.
 

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Solenoid part numbers

ZF : 0501 208 542
Land Rover : TJD000030
BMW : 24341422680

Just Google the numbers. ZF may try to sell you a kit with all eight solenoids.

Phil

P.S. I still think it's more likely to be your actual LUC at fault if you've never had the TC replaced :)
 

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Discussion Starter · #17 ·
Thanks for the part numbers and feedback Phil. I have no shifting issues, jolts, cattle grid noises (for now) :0, Smooth as butter except for the RPM fluctuations in the slip mode band. I am not running to the shop just yet, but its good to know what my options are and approach when the time comes. I guess I will keep an eye on things and drive in Sport mode if it really starts to bother me or gets worse I will take action. I am always in or under this vehicle knowing what I was coming into when I bought it so I will keep close ear on things :) Lets hope if it is the converter it doesn't take the transmission with it...:0

DDillinger, if you make any progress or care to venture out into reprogramming the ECU please let us know. I would be really interested to know how that goes...

Best
 

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Been driving it for a while now, and its been fine, I acctually started to think I had imagined the issues, and then, presto, going uphill 40kph, instant swaying. Next hill 50kph, same thing. A lot more than in previous video. And after that some cattle grid sounds. How is this possible ? The unit was brand new, they rebuilt the pump. is it possible to wear out a tv in 1000km ?
 

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Discussion Starter · #19 ·
Thanks for posting the update Shogo. I think your problems are pressure related as I mentioned in earlier posts I think the wiring harness and pressure solenoids are overlooked when overhauling the torque converter especially in your case. I am going to start with harness and Solenoids first when the time comes to deal with mine.
 
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