Review of the Sensodrive gearbox

If you have a Tip or Trick, some advice or you just want others to know something that is specific to the a Citroen C3 with an automatic gear-box , please, post it here. Includes the 4 speed AL4 with PRND and the 5 speed semi-automatic (SensoDrive) with '+ and -' controls.
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Tips for a Citroen C3 with an Automatic Gear Box

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Think: Auto not changing up or down, snowflake and sport flashing, flappy paddles and sensodrive not changing gear.
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Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
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The Sensodrive gearbox is a sort of hybrid gearbox. It is basically a standard manual gearbox that is manipulated by servo motors instead of physically done by the driver. There is no clutch pedal and effectively no gear lever.

While it may seem to have the advantages of both an 'automatic' gearbox and a manual gearbox, it also has both disadvantages!

There are 2 sophisticated servo units running the clutch, and gear selector inputs. For the most part these work very well and the system performance is typically satisfactory.
Being effectively a 'manual' gearbox the engine efficiency is, consequently, about the same as a manual. Traditional 'automatic' gearboxes have a device called a torque converter that substitutes for a clutch. The only problem is the torque converter is inefficient at transferring the engine power to the gears of the gearbox. Wasting power and fuel. The torque converter tends to give the power transfer a "rubbery" feel. A clutch is much better at this job. But as we know, the operation of the clutch requires deft manipulation of engine revs and clutch manipulation under all kinds of situations! So for this operation to work automatically, we are going to need a computer!
So what is the performance like? Well don't demand too much from it! The gear changes are fairly leisurely, meaning, if you are in a hurry, the gearbox isn't!
If you are after 'high performance' well, no. For average, day-to-day driving it works as well as a traditional automatic.
The system has 2 driving modes. Auto and manual. Auto changes gears automatically, like a traditional auto.
Manual requires the driver to select (gear) 'up' or 'down' from either the "flappy" paddles behind the steering wheel or the stick shifter on the floor console.
The Sensodrive will automatically change 'down' while in manual (if you forget) but it wont change will just keep reving out!
Of course manual gives the best over-all performance results but if you wanted that why didn't you buy an actual manual?
From a purely performance point the Sensodrive, in auto, gives a better result than a traditional auto. It doesn't "bang" or "slide" into gears and the engine feels more connected to the wheels. More responsive than a traditional auto.
In about 2004 there was an update to the Sensodrive software. Previously, when in auto, the gearbox would revert to manual mode (and stay there) if you touched the stick or paddles. The update caused the gearbox to go into manual when the paddles or stick were touched...for 10 seconds, after which it would revert back to auto. This was handy to override the gearbox temporarily but not have it go completely out of auto. Say, for example the gearbox wasn't changing down while you were going up a hill but you didn't want to press down more on the accelerator to get it to "kick down". However it would remain in manual mode for 10 seconds before reverting back to auto. This is too long a period! You then have to manually change up a gear because the engine is now over reving for too long. It should change up or down as requested by the driver but still remain in auto, and change gear automatically as required.
Another nasty habit the Sensodrive has is at "slow stops". You know, where you need to slow down for an intersection or round about (give way sign) and you may or may not need to stop or! The Sensodrive does not seem to pre-select first gear below a certain speed and tends to "depress the clutch" and coast. Not really a problem if you intend to stop. BUT if you are slowing down for that intersection and get a break in the traffic and you decide you are going to go! Nope! When you "put your foot down" the gearbox now has to go out of 2nd, select 1st and pick up the clutch...then you can go. Meaning if you get a break just in front of a ruddy great lorry and you decide to GO, you might wind up as a hood ornament! It's annoying and sometimes very dangerous! 99.9% not a problem...then that one time...
The Achilles heel of the system tended to be the clutch actuator. It is right at the front of the car and subjected to salt spray from salted roads in winter. This corroded up the workings and caused all sorts of system failures.
The other point was the clutch. It had a standard run-of-the-mill clutch...which wore out! Just the same as a manual car the clutch would eventualy wear out, a fact of life! But some Sensodrive owners didn't realize this and did not recognize a slipping clutch!
Being based around a computer, the Sensodrive system occasionally has "brain farts" and does something unexpected. Not dangerous or destructive but it does cause you to think "why did it do that"?
Then there was the shock and horror on the face of the mechanic when you drove your car in to get it fixed. "Nup! Don't know nuff'n 'bout them lady!"
The truth is that, with a little bit of knowledge, the Sensodrive was easy to maintain. It just got a bad rap.

Tips for driving a Sensodrive:
When changing gears manually, hit the paddles about 1/2 a second before you want the gear change. It takes a little over a second for the gearbox to select the gear. The Sensodrive gearbox changes DOWN gears VERY well! But the up changes...a bit sloppy.
When accelerating and changing up gears,either manual or auto, "freeze" your right foot on the accelerator during the gear change. If you "back off" or continue pushing down on the accelerator during the gear change the Sensodrive computer has trouble matching the clutch to the speed of the car. It's difficult to explain but the driver is in charge of the throttle but the computer is in charge of the clutch. If you have driven a manual car you know that you need to bring the engine revs up as you release the clutch (during a gear change). BUT not too much AND not too little! Easy to do when you are in charge of both but difficult if you are only doing 1/2 the operation!

Sensodrive or AL4 automatic?
That's a hard one. I live in Australia where they don't salt the roads and the Sensodrive clutch actuator is very reliable. But eventually you will have to spend the money to replace the clutch. In Europe the salting of the roads is very destructive in a lot of ways not least of which is stuffing up the Sensodrive gearbox. The Sensodrive relies heavily on electronics to perform it's task. Components, wiring and connectors are exposed to the atmosphere, on the outside of the casing and can be easily upset by environmental conditions.
Most of the components and electrical bits of the AL4 sit inside the casing in a nice oil bath. The AL4 has a life span of about 10 years. For a number of reasons it prematurely wears out. Typically, mechanical components like brake bands and clutch packs wear out. Before that, the gearbox tends to perform flawlessly. The auto box could be rebuilt but most owners would find it uneconomical, and ditch the car. I am not saying the auto box is irreparable at 10 years old. Just that problems start to creep in about that time.
On balance, for the "ordinary" owner, I would recommend the AL4. Only from a maintenance stand point. You will find it easier to repair and maintain the AL4 than the Sensodrive.
IMHO the Sensodrive gives better performance, but the 8@ll ache of getting it repaired is too much of a pain.

Just a few notes.
The Sensodrive was only available for the 1.6L engines. But the AL4 was available across the range. So it wouldn't be fair to compare a twin cam 16 valve 1.6L sensodrive to an 8 valve 1.4L AL4 and then say the AL4 lacks oomph!
Having 5 gear ratios, the Sensodrive might have done much better than the AL4 on the smaller engines?
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