Generic AL4 questions

[spider]

Honest these are not trick questions.

1. I do see occasional references to the updated solenoids. From what I can gather the newer ones are B.W and a software update for the trans ECU is *compulsory* for these. My question is simply this as if I had one I'm not sure I'd trust the dealer to fit them, but the question being what um 'state' is the transmission in with the newer solenoids but the old software ? Are you limited to 'limp' mode ? ie: 3rd and Reverse only ? Or do you have some functionality just nasty changes ?

2. Regarding the update, has anyone done the solenoid change themselves then presented themselves (well, their car!) to the dealer for the update and what was their response ? By this I mean were they 'happy' to do the update ? The reason for this is I've had one (not PSA) dealer refuse to do an update, they denied it existed even though I had (not with me sadly) some paperwork to prove it. Another dealer (different franchise same make) I spoke to on the phone knew about it and would do it for a price.

3. This might be a design question but um, filter ? From what I can gather it would need completely dismantling to gain any access to said filter. To be completely fair another makers car I owned about 5 years ago was similar there was no external (under pan etc) type filter. I realise its side mounted on the AL4. Another different maker had more a 'metal meshy' type filter actually.

Thanks.

[Mandrake]

If you are going to change the solenoids to the new types I would definitely update the software before fitting them, or at least before starting the engine. This can by done by anyone with a Lexia.

Most of the solenoids in an automatic box like this are "proportional" types that can open to varying degrees, especially those controlling the torque converter lock up track, rather than just fully open or closed. This is achieved by varying the average current to the solenoid, this is done by pulse width modulation where the current is rapidly switched on (to the maximum) and then off again, with the duty cycle controlling the average current thus the average position of the valve.

The new software works with both types of solenoids while the old software does not work with the new ones. I believe the difference is that the frequency at which the solenoids are pulse width modulated was changed, probably increased. My guess is that the new solenoids are "faster" acting than the originals, and that the original PWM frequency was too low for the newer types causing them to "chatter" instead of just assuming an average position. Increasing the frequency would prevent this chatter and would not cause any harm to the original "slower" solenoids, and is thus retroactively compatible with the old solenoids.

I would be very hesitant to run the new solenoids on the old software even to drive it to a dealer to get the software update done. If you don't have a Lexia try to find someone nearby who can do the update for you before the car is driven with the new solenoids.

[spider]

Thank you.

Its good to know (I should of asked that really) that the 'update' would work with the 'old' solenoids. I'd figured it would not or you'd have 'limp' mode.

I was *not* aware it was possible to DIY update it however given you need *ahem* to be connected to PSA to do this hence a spot of "open wallet surgery" at the main agent.

The frequency information does make sense too. I'm mostly aware of how they operate internally (how brake bands work for instance) although my knowledge really is mechanical ones not electronic, as in sets of sun/planet trains but this really is "old" I know as that will give 3 forward speeds.

[Mandrake]

If the software update is done in Lexia not Diagbox, which it will be if the car is pre about 2004, you don't need any connection to PSA... I've done a software update on the 4HP20 in a Xantia before with a Lexia with no connection. Diagbox will automatically launch Lexia when an older model of car is detected.

If the car is late enough that it only works with Diagbox and not Lexia then I'm not so sure - but I would still give it a try. It will either work or it will say that it can't do it. Perhaps a user of Diagbox on later model cars can pipe up...

You don't say what model and year car the gearbox is from ?

[spider]

Thank you.

I do have Diagbox (although its still at v7.04 I think I'm not sure) Last time I used it was for the trusty 106 which I sold about 3 years ago now. Hmm.

To be 100% the questions were not tied to a specific vehicle although I'd probably be looking at a pre-plexed car anyway late Xantia or suchlike.

[Mandrake]

Diagbox 7.04 is fine. That's very near the version I use with my Xantia.

If the car is a Xantia or early C5/Xsara or any pre-multiplexed model really then Diagbox will just launch the old Lexia software (with its Playschool yellow and grey interface) when you choose the model of car. As long it launches Lexia you should be OK to update the gearbox ECU software.

It will be in the "downloading" section in Lexia. Although the Lexia software does have the option to "Phone Home" to PSA to download newer software updates for ECU's, it comes bundled with all the ECU software updates already, as Lexia has not been updated in years now. (There are no newer software updates to download than the ones it already has built in)

It goes without saying that a software update for an ECU like the gearbox ECU does carry a small risk of going wrong and bricking the ECU, but only if you're very unlucky. The most important thing is not to let the update process get interrupted. Don't let the cable come loose, or the battery on the laptop run out in the middle of the process or you could end up with a brick.

[spider]

THank you.

I was not aware it had the required updates already present. This partly explains its um "bulk" though. I'd assumed it wanted to get them from PSA like the older Diag2000 units did, well from a CD if memory serves.

I'm aware of the dangers as I see it the same as a PC Bios flash update, anything goes wrong halfway and its over. (exception here being you can recover most PC's) but yes I know what you're saying. I'd suspect it is EEPROM memory being used in the ECU I've not looked.

[Mandrake]

If you poke around in the downloading section in Lexia, there is a full list of the ECU software updates available and built in and a very brief (a few words!) description of each one and what it was for. I remember seeing the AL4 update in there. The 4HP20 got an update that changed the warmup behaviour when cold, causing it to hold first gear a bit longer. But like PC software updates there may well have been other bug fixes that they did not list.

I think you can browse to this list even when not connected to a car. Just connect the Lexia interface to the laptop and enter a valid VIN number for an early car, it should launch Lexia without complaining that it can't find the car, then go into the downloading section and browse around until you find the list. (I don't have it in front of me to tell you exactly where)

[spider]

I'll take a look later thanks.

I know where you mean. I recall looking at this for the 106D (as it was the TUD5B with the electronic advance pump) but there was nothing listed from what I recall.

[spider]

I'm not even more confused after reading some random topics on here.

I'd (assumed) that the AL4 was the *replacement* for the 4HP unit.

I'd assumed (correctly) the AL4 is fully electronic.

AL4 is obviously 'no dipstick' and "plug inside a plug" for level, I've checked a few in the dim and distant past on a couple of 406's. It is a pain but I can say its a *lot* easier than trying to do this job on the VW 01M transmission (I'll spare you the details)

I'd also assumed ( help ?? ) the 4HP series was completely mechanical, the same unit was fitted to the 405,205 and earlier 306. 4 speed mechanical auto trans, early ones with two drain plugs and all of these units have a conventional dipstick.

From what I am reading ( help ?? ) lower powered engines may have the 4HP unit but the larger ones (larger HDi and say the V6) will have the AL4 ? , unless this is vice-versa.

Yours, slightly confused...

[Mandrake]

I'd (assumed) that the AL4 was the *replacement* for the 4HP unit.

I'd assumed (correctly) the AL4 is fully electronic.

[...]

I'd also assumed ( help ?? ) the 4HP series was completely mechanical, the same unit was fitted to the 405,205 and earlier 306. 4 speed mechanical auto trans, early ones with two drain plugs and all of these units have a conventional dipstick.

From what I am reading ( help ?? ) lower powered engines may have the 4HP unit but the larger ones (larger HDi and say the V6) will have the AL4 ? , unless this is vice-versa.

Yours, slightly confused...

Yep you are pretty confused.

Both AL4 and 4HP20 are fully electronic computer controlled gearboxes.

One is not a replacement for the other as the 4HP20 is made by ZF and the AL4 is made by Siemens! So they are competitors, but they are not in the same performance segment.

They are broadly similar in design on the principle level but all the details differ. The AL4 uses brake bands while the 4HP20 does not use any brake bands. (Instead it uses more robust brake clutches that are the same design as the drive clutches)

The 4HP20 has a three mode torque converter lockup which includes closed, open and partial (50 rpm) slip. As far as I know the AL4 does not support a partial slip mode.

Finally the 4HP20 supports way more torque and power than the AL4 - the AL4 is the lower powered unit that is designed for 2 litre petrols for example while the 4HP20 is designed for the 3 litre V6 and similar engines.

Early 4HP20's like mine have a dipstick much like an engine oil one which makes it very easy to fill and check the level - you fill through the dipstick hole. Later 4HP20's have no dipstick, instead you fill via the air breather hole and there is a level plug on the side instead a bit like a manual gearbox. Both versions have a standard drain plug like an engine sump.

The AL4 on the other hand uses a coaxial "plug inside a plug" arrangement for the drain plug that doubles as as a level drain plug. I'm not sure what orifice an AL4 is filled via.

Hope that helps.

[spider]

Thank you, that's great.

The 'confusion' stemmed as I'd assumed that all 4HP's had dipsticks hence they were all the 'older and not fitted after 98ish' units.

I'm aware of that 'level' check procedure for later 4HP's then from other marques, although they involve measuring the oil temp (typically the level will only be right for the 'side plug' at the specific temp + / - 10c) at least for other brands who shall remain nameless.



One more question (sorry) do severe 'limp' modes vary between these designs ? I'd expect 3rd and Reverse to function if the electronics fail. Obviously no t/c lockup and not a lot else. I'd hope that with dead electronics a vague way of driving it home carefully is possible...

EDIT... Edited slightly to tidy / clarify.