Citroen C6 Gearbox Problem

[Alexander Stern]

Hello everyone,

I own a Citroën C6 2.7 HDi from 2006, and I’ve noticed some gearbox issues when it gets warm. After about 20–30 minutes of driving, it starts revving too high in second gear and then shifts into third with a bit of a bang. Sometimes it also happens between third and fourth — it feels like the clutch is slipping slightly.

I’ve already done an oil change (without flushing, just drained and refilled), but the problem is still there.

Could this be related to the valve block / valve body? Has anyone here had similar experiences or replaced it? I’d really appreciate any advice or shared experiences about what helped and what to expect from the repair.

Thanks in advance!

[mickthemaverick]

If you just drained and refilled do I take it that you haven't replaced the gearbox oil filter?

[Paul-R]

How many times did you drain and refill the gearbox? Over what period?

[moizeau]

Sounds like the valve block. They can be changed, there is info here somewhere written by Marc. My 407 does iy between 1st and 2nd sometimes when warm, also 'flares' between 5th and 6th. You can't change the filter as far as I'm aware without removing the g/box.

[mickthemaverick]

Good point Pete, I've got used to external filters on the cars I have at the moment!!

[Alexander Stern]

If you just drained and refilled do I take it that you haven't replaced the gearbox oil filter?

It was done by a service in my area and they changed the filter also.

[Alexander Stern]

How many times did you drain and refill the gearbox? Over what period?

Only once.

[Alexander Stern]

Sounds like the valve block. They can be changed, there is info here somewhere written by Marc. My 407 does iy between 1st and 2nd sometimes when warm, also 'flares' between 5th and 6th. You can't change the filter as far as I'm aware without removing the g/box.

In the invoice they put the filter also. But i don‘t think they removed the gearbox.

[MGmike]

How many times did you drain and refill the gearbox? Over what period?

Only once.

It needs to be done at least three times to dilute all the fluid in the torque convertor unless they used a special adaptor to drain and refill at the same time.

I also think you have a valve block issue which is easier and cheaper to replace than having a full gearbox overhaul.

[Stickyfinger]

Sounds like the valve block. They can be changed, there is info here somewhere written by Marc. My 407 does iy between 1st and 2nd sometimes when warm, also 'flares' between 5th and 6th. You can't change the filter as far as I'm aware without removing the g/box.

In the invoice they put the filter also. But i don‘t think they removed the gearbox.

I would return to them and ask... HOW did you change the filter ?....(it can only be changed via strip down/box out = they LIED to you).
All they did is change some of the oil in the gearbox....due to a large amount being held in the converter all that happens is the dirty oil is slightly less dirty.

The Gearbox is VERY sensitive to the EXACT TYPE of oil, many garages/gearbox service centres use "generic oil/backward compatible (specifications) oils".....there is a long history of problems developing/getting worse after these "non specified" oils being used.... Again, I would try and find out what they used (exactly/specs) to refill your gearbox.
You need to ID the gearbox number/item code....this should be on a sticker on the box.
I would ALWAYS reject any "Multi-use/Compatible with Multiple Spec" oils.

Correct type of oil discussed here...as a rule, contact Citroen win you Vin number and ask them to tell you exactly the oil spec /type used for your gearbox.
viewtopic.php?t=58134&start=60

A common method is to drain and refill 3x......less common is a trip to a Volvo dealership (they have a fitting I understand/same gearbox is some S60's etc) and have it changed whilst the car is running, a "power on" flush which also exchanges the oil 100%. (I have never done this/been to Volvo....maybe some specialists also do this)...........this is more expensive/uses more oil.

Info here....
viewtopic.php?f=3&t=58134&start=45#p543115

When replacing the valve body (recommended) AND after an oil change, Volvo for example, say you should reset the gearbox counter and allow the gearbox to "Relearn" the correct settings.............This is normally done via the cars systems connected to the garages service computer.



Often a correct oil change/dilution x3 works and the box returns but also be aware that many Gearbox's do not return to normal.....it always strikes me as a bit of a lottery with 80-100.000miles being the "hit point"

1. The AM-6 Gearbox can be rebuilt, not cheap.
2. 2nd hand ? ONLY IF it is low KM/Miles or you just inherit the same problem a bit later/soon.
3. Take a chance,,,,,,,have the valve body replaced/power-on flush....enter the lottery (a good bet/what I would do)
4. Take a chance and do a "power-on" flush of a 3x drain/refill and gearbox Reset/Relearn

[Alexander Stern]

Thank you all for the replies. They all very helpful.