Xantia V6 autobox behviour

[citroenxm]

Hi fellow Xantia V6 drivers..

Im curious to your experiances with your auto boxes on V6 Xantias..

Mines fine most of the time, however, it can BANG badly and shudder the car when going from P to Reverse, however, from N ro Reverse is not so bad... I guess it could be a valve sticking..

My other query is over run, when im going down a hill, or on level over run, the box appears to disconnect drive, and the engine goes to idle, sometimes, she will change down a gear for engine braking but not always...

In sort, she does behave properly ONLY when accelerating, she'll hold a gear unless I lightly apply the throttle then she changes up as she should, this I beleve is normal for SPORT..

The gearchanges UP the box is very smooth, especially at full throttle and 5600 RPM, the 2 to 3rd change is amazing...

My biggest concern though is the over run, and Reverse engagement.. is she behaving or not??

I was going to make this a PM, but decided a public topic may give better responses...

Thanks

Paul

[DickieG]

My one engages/changes gear smoothly all the time, difficult to comment on the downhill element due to the amount of variable factors.

[CitroJim]

Hi Paul,

I understand how this is causing you a tad of perplexation but let me assure you, everything you see is normal.

The bang from P to reverse is to be expected. In P or N, clutch B is engaged in rediness for the next gear selection. This means the annulus of the epicyclic gearset is rotating forwards more in anticipation of first rather than reverse gear. When Reverse is selected, Brake D engages to stop the rotation of the annulus - hence bang as reverse is now engaged, the annulus has been stopped dead and sudeenly everything that was happily freewheeling in a forward direction is now going backwards.

That said, the bang should be quite soft and not enough to make you jump.

Overrun. That's normal. It depends on the TC lockup status. The TC is unlocked in that condition and you will see it happen when you come off the throttle and coasting along a flat road. The auto-adaptive does it to save fuel thrpoug a lowering of rolling resistance. If you brake you'll see the lockup come into effect and engine braking will commence. The auto adaptive does it's best but at the end of the day it's just a computer...

Yep, I'd agree, the 'box is beautifully smooth with seamless changes when accelerating briskly but this is about the only time. Very gentle acceleration will make upchanges a bit notchy at times. Have you noticed that sometimes around 30mph the 'box will sometimes change up a bit slowly to 3rd?

Downchanges can be a bit. I find under heavy braking to a halt with the TC locked up that the 2 - 1 change can be a bit sharp. It seems to me that the auto-adaptive holds on to TC lockup just a bit too long to make it really smooth.

Interestingly, this all seems a bit of a feature of early MK1s. Remember ours were the first cars to have the 4HP20 and I know mine has a very early software revision. The MK2 I have driven did not show these effects to such an extent so I wonder if a later version of software would help. I'm sure the early auto-adaptive algorithms can be improved upon and I reckon it was in later versions.

But basically Paul, all is really quite fine with yours. The gearbox is not about to bid a fond farewell any time yet...

On a happier note, have you experienced the double downchange yet or the really smooth kickdown when you want to really press on Fantastic isn't it!

EDIT: a tad of wear in the intermediate gears and diff crownwheel which leads to a bit of backlash can magnify all these effects. Mine is a bit worn in these areas.

[Stempy]

Apart from the banging into reverse sounds about the same as mine. When I was shopping around for a V6 I test drove a Mk1 which seemed to bang into reverse a bit hard, one of the things that put me off it, but otherwise the box was fine.

[citroenxm]

Ok guys, thanks, that helps a bit, I find it strange, because the other Green V6 that David Hallworth has, does NOT do it, thats all why I quireied it, and I expected it to go away with a bit of use, but it hasn't...

Yes the DOUBLE kick down is amazing, Ive taken 4 people out in her, and they have ALL said O M G! Amazing, and revs to 6500rpm with an auto box!!

Mind you, I can get my V6 XM, thats mechanical box and kickdown, on the PRV V6 12v to double kick down...

I noticed theres no kickdown cable on the 4HP20, this must be due to the electronics???

A fluid change wont go a miss at all then??

B T W, Are you going to the Rally on the 12 september Jim??? I AM going, and have booked my days off for it..


Cheer
spaul

[CitroJim]

Hi Paul,

The kickdown is all electronically controlled and part of the auto-adaptive. Just like a mechanical kickdown though, it's vitally important to ensure the throttle butterfly is completely closed on idle as this determines a signal sent to the gearbox ECU to say the butterfly is closed, open or WOT (Wide Open Throttle). The ECU uses all three conditions for varous auto-adaptive tasks. It can be checked on a Lexia.

A gearbox oil change is well recommended. Do three partials to ensure as much of the oil oil as possible is out. When refilling, check the level with the gearbox very hot. Lervel should be between min and max markers on the dipstick but never above.

Yes, I'll be at the CXM rally on the 12th. It's practically on my doorstep and I have it already booked in my calandar.

It'll be great to see you there

[Sid_the_Squid]

I'm a bit late on find this this thread, however I'll add my experience in. I experience pretty much everything you describe except the reverse bang, frequently there will be a slight jerk going P-R but not a bang.

I've also noticed gear changes are smoother at higher revvs or rather greater throttle.

In short like most have already said, your car sounds fine

Oh and yes change the box oil, like Jim says do a few changes, as each time its only a partial change.

[xantia_v6]

Reading the first post, I don't think it describes typical behaviour.

it can BANG badly and shudder the car when going from P to Reverse, however, from N ro Reverse is not so bad...

Mine have never done that, except in emergency limp home mode.

My other query is over run, when im going down a hill, or on level over run, the box appears to disconnect drive, and the engine goes to idle, sometimes, she will change down a gear for engine braking but not always...

Mine will occasionally freewheel on overrun, but only, I think, if the transition to overrun is very gentle, normally it just stays in the same gear. In any case, touching the brake always makes it change down (which can be irritating if you are just matching speed with the car in front).

In sort, she does behave properly ONLY when accelerating, she'll hold a gear unless I lightly apply the throttle then she changes up as she should,

I am confused by that part, are you saying that it changes up when you increase to light throttle, or decrease to light throttle?

My biggest concern though is the over run, and Reverse engagement.. is she behaving or not??

Maybe I have been driving mine too long (90,000 miles in the mk1 and about 2000 miles in the mk2), but your complaints sound strange to me. Maybe we had better swap cars for a day Nope, you are on the wrong side of the island.

The things I notice about the 4HP20 on both of mine are the interminably slow kickdown when not in sports mode, the over zealous engine braking when going downhill after touching the brake, the occasional rough upshifts at light throttle and occasional jerky downshifts from 2 to 1 with no throttle.

[CitroJim]

In sort, she does behave properly ONLY when accelerating, she'll hold a gear unless I lightly apply the throttle then she changes up as she should,

I am confused by that part, are you saying that it changes up when you increase to light throttle, or decrease to light throttle?

Yes, that does sound a bit odd on reflection. Mine will change up very rapidly in normal (economy) mode mtre or less irrespective of throttle position.

Thing is, upchanges can be so seamless and with the TC unlocked and doing it's job it is hard to know sometimes just when it has changed.

I reckon a Lexia session would not be a bad idea, following an oil change. The Lexia will confirm exactly what is going on and on a road test will tell you what gear it is in, how much the TC is slipping at any given time, what mode the TC lockup is in and what map the ECU is currently following. I'd also be inclined to re-initialise the ECU so that it re-learns the valve block and clutches.

If you bring it to the CXM rally Paul, we can do that but I guess you'll be bring an XM for that show! You can have a drive of mine there though and see how it compares.

Howe many miles has the car done Paul?

[citroenxm]

Hi Jim,

Unfortunally, my XM of any viriety wont be making an apperance, Im currently XM'less as far as being legal goes..

I wont be bringing the V6 either, shes not tidy engough yet, the wing has been sprayed, but is not fitted yet, so shes not going on show untill then..

I have worked out on assumption that shes only done about 65k... 42k on old clocks, which the stamped service history goes up to, and the clocks in the car showing about 23k... so I am assuming just 65k..

To be honest, as far as seats, door closing, pedal rubbers etc etc go, she feels like that all shes done too...

I think I need to invest in a Lexia both for the V6 and other HDi projects..

Paul
Paul

[CitroJim]

I wont be bringing the V6 either, shes not tidy engough yet, the wing has been sprayed, but is not fitted yet, so shes not going on show untill then..

I'd not worry about that at all Paul. My V6 is by no means concours. In fact from some angles she's really quite scruffy..

"Rat Look V6"