Auto box slippage - Citroen C5 - machika
Our C5 recently had an update to the engine and gearbox software, not at my request I should add, as it was done as part of an attempt to cure an engine management fault. However, I now suspect there is something amiss with the gearbox, as I appear to be getting slippage in second gear.

At around two thousand revs, or just above, the rev counter either stays static or falls back slightly, before picking up again. I assume this is not normal practice for an auto box? It doesn't happen in any other gear. I am beginning to wonder if it is anything to do with the software update, as I can't recall it happening before, and I began to notice it after the update was carried out.
Auto box slippage - Aprilia
If you were getting slippage (known as 'flare') then the revs would briefly rise rather than fall. Normally this is noticable when the box upshifts - i.e. the engine revs 'flare' between gears rather than experiencing a smooth 'fall of the needle'.
Auto box slippage - machika
If you were getting slippage (known as 'flare') then the
revs would briefly rise rather than fall. Normally this is
noticable when the box upshifts - i.e. the engine revs 'flare'
between gears rather than experiencing a smooth 'fall of the needle'.


Well, the revs do rise, then fall back or stay static, before rising again, then the gearbox changes gear. Why would it be doing this?
Auto box slippage - Citroen C5 - Timaru
Is this the ZF box or the PSA box?
Auto box slippage - Citroen C5 - Aprilia
I'm assuming its the PSA AL4.
Auto box slippage - Citroen C5 - machika
I don't know what make the box is.
Auto box slippage - Citroen C5 - Timaru
If you have the V6 or 2.2 Hdi it will be the ZF 4HP20 box. This thing does all sorts of cleaver things some of which replicate the symptoms you describe.

If you Google - ZF 4HP20 adaptive - there is a fair amount of information, mainly on "Pug" sites but as Pug & Cit are from the same stable I've always assumed the info. is interchangeable.
Auto box slippage - Citroen C5 - machika
Would the behaviour I describe not be signs of a fault then? The technician at the local main dealer says there is no fault with the gearbox. If so, it is strange that it only does it in second gear.
Auto box slippage - Citroen C5 - Aprilia
If the engine speed is varying but the road speed is not changing then something is slipping. Obviously the torque convertor behaviour needs to be taken into account, but yours doesn't sound like its the TC. Take it to an auto-trans specialist for a test drive, normally they will not charge for a 10-15 minute test run. Most main dealers know very little about auto trans.
 

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