exchange Gearboxes

I hope you good people don't find me annoying, but so far your help as taught me a great deal and I thank you so much for that however it seems my gearbox issues are rather terminal so I haven't been able to resolve my issues and seeking the next possible step in my journey to recovery of my 2006 C3 New Shape model, so here's my next question, I've been offered a good working replacement transmission extracted from a 2003 C3 complete with ECU, so can anyone tell me if this would be suitable to drop into my car or any suggestions? and please don't be rude lol. Thanks in advance.

Hi

Many changes were made in 2006 for the facelift model. Systems went full CAN which were previously CAN-VAN.

The chance the ecus are compatible is slim.

I've not done that swap, but if I was, I would pick a auto gearbox from a 2006 to 2009 model to replace one from 2006.

It will be the ecu that is the issue (if there is one)

Thanks so much C3CAR .. The problem here in Australia is the lack of availability of new and second hand parts and the Postage from overseas is outrageous and slow, well the 2003 box is the only one on offer .. maybe it will marry to the existing 2006 CPU (which seems to be ok)
Thanks again for your support.

Was there something physically wrong with your autobox? Too expensive to re-build?

There shouldn't be a problem swaping the boxes. Up 'till 2002 the electrovalves and programing for the AL4 were different. The electrovalves were made by Borg Warner. They had white electrical connectors and different PWM timing. Now they have black connectors and are made by the Chinese. To my knowledge all the auto boxes put in the C3's up to 2009 (2003-2009) are basically the same. They may have newer software revisions in the ECU but should still be compatible.

The gearbox ECU is connected to the (engine bay) CAN BUS and this does not change from CAN/VAN (2003-2005) to CAN/CAN (2005-2009) vehicles. You can always take the gearbox ECU off the 2006 gearbox and put it on the 2003 gearbox. It might take a couple of hours for the box to re-learn the adaptables, but it should be fine. Of course the question is: is the 2003 box physically OK? Dunno!

Be very careful IF you take the ECU off the gearbox. The single bolt on the front of the bracket can strip the aluminium threads out of the gearbox case. Loosen the two bolts on the side of the bracket first and support the bracket when you undo the single bolt!!! The bracket is heavy and can be twisted. This will put pressure on the bolt threads and cause damage.

WARNING: rant ahead!
Why are there 276 (not really) video clips on Youtube on how to COMPLETELY strip down and then rebuild an AL4 gearbox, pros and cons of the gearbox ETC , but not one of them speaks English????!!!!!
Why are most of these videos from poor South American or Asian countries with a GDP equal to a small child's piggy bank?? Where, it appears, they are rebuilding the gearbox in someones kitchen! But in a first world country it's "too expensive" to rebuild the gearbox??? Just buy another car?! WTF!!!
Sorry, rant over.

Thanks once again Ozvtr, and your rant is completely my sentiments also, rather frustrating actually. and I
certainly appreciate your response ... very generous. oi oi oi

Just like to send special thanks to Arfur Dent, Jagpurr and most helpful, Ozvtr for their help
on my Gearbox issues .. The problem turned out to be the wiring loom between the EV and the ECU
which I replaced (second hand from a 2003 AL4 but in as new condition) Cheers .. Baldseas-54.

Thanks Baldseas-54 for getting back to us.
We can only help others from knowledge deposited on this forum. If we don't get a result...we haven't learnt anything.

Did you replace the loom as a matter of course or did you find a physical problem with it?

I am in the process of doing a new "how to" to replace the valves, including resetting the selector cable. Do you have any tips or hints for me?

After replacing the two main EVs with new units (generic) also replacing the two rubber seals before reassembling the hydraulic block, I noticed when refitting the loom to the solenoids that these fitting were loose, without resistance on the five side valves, I had not removed the loom (harness) from the gearbox itself and thought this normal, after full assembly and a road test which went rather badly as second gear was not engaging and limp mode activated I performed a diagnostics with Lexia3 which stated this “Temporary Fault” Pressure Regulation ( difference / setting) so upon removal of the Hydraulic block once again, a very frustrated old fart (me) decided to replace the Loom given the poor fitting clips were still worrying me, I had purchased a second hand “Box” from a 2003 model C3 and extracted the loom, which was a great experience in itself, had I not done so I don’t think I’d have succeeded in removing the loom fitted in the engine bay also when removing the clips I received a heart warming “click” as did when reinstalling! Reassembled and after adding 1.6 Ltr. Of oil and with a very rewarding road test. The only fault showing on dash screen is “Antipollution faulty” otherwise a perfect response from the AL4 .. the antipollution faulty is another story.
My conclusion is my fix was more trial and error rather than good deductions or fault finding, however I’m much richer for the great help and the experience.
I hope in some way this information may be of use.

Baldseas-54 wrote: ↑Thu Aug 19, 2021 4:54 am also replacing the two rubber seals before reassembling the hydraulic block,

The two o-ring like seals at the bottom of the valve block mount? Did you get new ones from Citroen?

Baldseas-54 wrote: ↑Thu Aug 19, 2021 4:54 am I noticed when refitting the loom to the solenoids that these fitting were loose,

These little connectors are usually quite tight (as you later found out). What do you think happened to them to make them loose? Was it just the 5 on the sides? Not the one on the bottom and/or the 2 on the back? Or were all of them loose?
Did it look like the gearbox ECU had been disturbed or do you think you were the first in there?
On the first one I did, the gearbox ECU had been disturbed as the single ECU mounting plate screw on the front of the transmission was at a wonky angle and chewed out. I have since discovered that screw , somehow, gets the thread damaged in the factory!! That in turn causes damage to the very soft aluminium thread in the transmission bell housing. If you are not careful when removing or re-installing that screw, you risk destroying the thread in the transmission!

Sorry I took so long responding to your Questions, First of all the gearbox had been tampered with before (By me three times and a Dealer in Hervey Bay Apparently) and at some stage it may have been over heated and this possibly could cause the looseness in the EV clips, or a bit of both maybe, and yes it was only the five side clips that had issues. maybe this rules out the overheating ... when I purchased the car the Fan didn't function and was prone to getting a bit hot at idle, I replaced the fan of course. (from the UK)
I found the same problem with the ECU mounting but fortunately (and it had been removed before) it didn't strip the thread and I quickly found loosening the two side bolts first solves the problem.
I purchased the two rubber "o" rings from Brisbane City Automotive via Max Rood .. Parts Ph.(07) 32531450 or parts@brisbanecityautomotive.com.au (cost about $5 each) I did buy spares just in case.
I hope this helps and only too happy to be of service.