Knowing the issues that repeatedly seem to be emerging with the ZF 6HP26 Mechatronic unit – and in particular the proportional solenoids - we should consider the possibility that the adaptions have been compensating for a fault with one (or more) of the solenoids such that, when they are zeroed, the full extent of the fault is brought to light. If that's the case, the problem is with the solenoid(s) not the diagnostic kit.

Click image to enlarge

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Yes but it's better to leave well alone isn't it ?.
The Auto guy I used says a little experience is dangerous using these scan tools.

^^^^ Agreed. I accept that it's not the diagnostics tool that's caused this but whilst the gearbox was compensating it worked and this has just caused a whole heap of trouble.

I have no clue what I'm doing in this area and I'm the first to admit it! 2006 4.2 SC
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I do agree with Phil his knowledge is unbelievable on these boxes and I now understand that there must of been a fault before and as Phil says the ecu adaptations where masking it. It may of lasted a week or a year if I hadn't of messed it always happens at the worst time though. The difference between theory and reality is that in theory it will work.

How many miles has it done, Dave?

What's the next steps? 2006 4.2 SC
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SKOT wrote:

^^^^ Agreed. I accept that it's not the diagnostics tool that's caused this but whilst the gearbox was compensating it worked and this has just caused a whole heap of trouble.

I have no clue what I'm doing in this area and I'm the first to admit it!

It's done 126,000 I was going to do some ringing round today but havnt feeling a but deflated with the car now but it is the only problem I've had and I suppose it's piece of mind to know the gearbox is ok when it's been done. But I've parked it up on the drive and will deal with it after Christmas as no one is going to be able to look at untill then anyway will Keep you all up to date.

Just a thank you to Phil and Glynn they have been a big help and I couldn't believe how good people are on this forum The difference between theory and reality is that in theory it will work.

Also consider going the auction route.

I've put money into a car with miles on it and a catalogue of other things went wrong. It ended up being a total money pit. If it's done you well, there is maybe merit in walking away and starting afresh.

Just my 2Ps worth! Good luck with whatever you decide. 2006 4.2 SC
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Last edited by SKOT on 23rd Dec 2013 7:48pm. Edited 1 time in total

RRPhil wrote:

Knowing the issues that repeatedly seem to be emerging with the ZF 6HP26 Mechatronic unit

Phil, is the ZF 6HP26 not as bullet proof as first thought then? Have you seen many of these? Any observations on the cause? 2006 4.2 SC
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I understand what your saying Scot. I'm going to stick with her I have not had it long and it took a while to find apart from the gearbox I have a load of recipts of work that's been carried out its only had one owner and is mint. I couldn't believe it when I found her it has a FBH too with remote and it works a small comfort I suppose The difference between theory and reality is that in theory it will work.

SKOT wrote:

Phil, is the ZF 6HP26 not as bullet proof as first thought then? Have you seen many of these? Any observations on the cause?

The 6HP26 has been in production for thirteen years now and I’ve heard of virtually no issues relating to either mechanical or hydraulic faults with this transmission, which is amazing.

The only problems I’ve read about or come across seem to relate to either software (adaption) or solenoid issues, neither of which requires the transmission to be removed from the vehicle to fix.

Automatic transmission repair shops (in the UK, at least) believe it isn’t economic to start stripping down valve block assemblies so they just replace the whole unit. In the case of the 6HP26, ZF have encouraged this by not making the individual parts available anyway (and, until recently, that included the solenoids), whereas on previous transmissions like the 5HP24 all the blocks, spools and springs were available separately.

Also on the 6-speed, unusually the individual solenoids are set up at the factory to match the required pressure and flow characteristics for a given valve block as the transmission ECU is an integrated part of the valve block assembly

Click image to enlarge

hence ZF claim that the Mechatronic unit should only be replaced as a complete unit. However, from the previous experience of others, I know that after resetting the adaptions following solenoid replacement the ECU successfully relearns the settings for the new solenoids very quickly.

In summary, I think that the 6HP26 is pretty bullet-proof and that any issues that do occur are generally pretty simple & relatively inexpensive to fix. Certainly more reliable than the 5HP24 in any case. I won’t even compare it to the 5L40-E which, as we all know, is actually made from cream cheese and cotton wool and is unlikely to last beyond 80k miles in a Range Rover.

Phil

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Based on my experience with the 3-4 shift fault, the resolution was "just replacing the coils or proportional solenoids". It is a relatively cheap solution (compared to a full gearbox replacement).

Phil is correct, the 6HP box is used in lots of cars of different brands so there are a LOT of them out there with no issues. That is why it is hard to diagnose issues when they crop up.

My parts supplier (specialized in just auto boxes) in the Netherlands also confirmed that the solenoids are a weak point and one of the first things they replace when a box with problems comes in.

Worst case for you would be that you replace the coils and the problems don't go away, and then a full mechatronic replacement could be the next stop.

I do note that your box/car has done a fair amount of miles but no idea how many miles these boxes can do before the clutches/brakes need replacement. Not that the type of fault you are getting seems to have anything to do with that.

I would take the "risk" and just replace the solenoids and maybe combine it with the fluid/filter change as well and see how it does. Then do the adaptive value settings drive cycle that JLR suggests (see my gearbox thread, kind thanks to Phil) and within a few weeks you hopefully have a supersmooth box again.

Good luck. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Very useful feedback. I read it (and maybe I've misinterpreted it) that Av_dave is planning to replace the whole 'box. You are saying he may not need to do that? 2006 4.2 SC
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Hi Skot, absolutely, first just replace the solenoids and do the fluid and filter as an option. I suspect that the gearbox is fine it is just the solenoids that seem to be causing the issue.

If the gearbox is gone then worst case he spent some 280 GBP (if you can order them in Holland they are 235 Euro plus postage).

There is another member on the forum that is going through exactly the same at the moment and I am hoping ot hear from him soon whether the solenoid change has done the trick !!! MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Im not so sure about just replacing this and that within the mechatronic unit at this milage, mine had its mechatronic sent to a mechatronic recon centre in Luton, repaired and tested etc, when it came back and was refitted it was no better !.
Then a brand new mechatronic unit was fitted, result - perfect as new gearbox behaviour.