Xantia diff

RStacey · Post by **RStacey** » 07 Aug 2006, 08:46

99 Xantia Hdi 110

I have been trying to locate the source of a "clonk" when going from overrun to acceleration a visa versa - it sounds as if back lash is being taken up in the right hand driveshaft but I cant find any play in either the outer or inner joints, the centre bearing or any of the suspension joints/bushes (I've checked both sides). There is however approx 15mm of backlash (measured on the wheel) in the diff and if I spin the the wheel either way, stop and then spin the wheel the other way there is a distinct metalic noise from the diff as if something is falling back into place - is this normal? Apart from the "clonk" there are no other symptons and the car drives perfectly.

Any ideas would be welcomed

Post by **Peter.N.** » 07 Aug 2006, 09:47

There is always a certain ammount of backlash in the final drive but it doesn't usually result in any noise. Have you investigated the engine mountings? the bottom one is favourite on the XUD but your engine might be different.

alan s · Post by **alan s** » 07 Aug 2006, 10:32

I was recently asked by a Citroen car wrecker if I had replaced the "pins" in the diffs of the 2 Xantias we have or if I knew if they had been replaced as they tend to get loose and come out via the side of the housing apparently.

Has anyone else heard of this and if so, any chance of a rundown on what the symptoms are as I have the feeling this is the kind of thing you'd expect they might do. Also a rundown on what's entailed in doing them would be handy too.

Alan S

Kowalski · Post by **Kowalski** » 07 Aug 2006, 11:10

alan s wrote:I was recently asked by a Citroen car wrecker if I had replaced the "pins" in the diffs of the 2 Xantias we have or if I knew if they had been replaced as they tend to get loose and come out via the side of the housing apparently.
Has anyone else heard of this and if so, any chance of a rundown on what the symptoms are as I have the feeling this is the kind of thing you'd expect they might do. Also a rundown on what's entailed in doing them would be handy too.

Alan S

My first reaction to that can't really be posted here....

Its not completely unheard of for PSA gearboxes to come apart, they're pretty reliable and long lasting as long as they have the right oil in them. I've heard of maybe 1 PSA gearbox losing its diff, its a pretty rare occurance.

alan s · Post by **alan s** » 07 Aug 2006, 12:48

I've heard of it before not only on Cits but also some model pugs. (306 from memory) and it is quite a messy thing when it happens as the bits and pieces come right through the housing.
Maybe it could be something more prone to hotter climates or perhaps caused by long hot drives as in my case, I have driven cars over 1300klms at a stint on a couple of occasions in the past 6 weeks or so.
Either way, the guy who mentioned it has had it happen to cars he's bought in as well as his sons car, so out here not all that uncommon apparently.

Alan S

RStacey · Post by **RStacey** » 07 Aug 2006, 15:39

all this talk of exploding diffs is not filling me with joy - what pins is he talking about? - I cant see from the Citroen exploded

diagram what he means.

ps all engine mounts are ok

alan s · Post by **alan s** » 07 Aug 2006, 20:35

I don't think it's a real big deal providing if this is the problem it's attended to prior to failing.
IIRC, he made reference to the planetary gears so I suspect either it is the shafts that the sun and star gears run on or something associated with retaining those shafts.

Alan S

Post by **CitroJim** » 07 Aug 2006, 21:37

Some of the 205 Mi16 brigade has had this happen but only when doing very, very silly things. Those same lads reckon that generally the BE3 'box is virtually unburstable, certainly in normal use..

I recall a short tale once in Car Mechanics of a 405 that had its sun and planet gears exit stage-left complete with lurid photos. There is always an exception to the rule.

Stupid question this but has it the right amount and viscosity of oil in it?

RStacey · Post by **RStacey** » 07 Aug 2006, 22:11

I checked the oil 2 days ago - drained out 1.9 ltrs of clean oil and replaced with the same amount of new oil so I dont think there's a lubrication problem. The gearbox is not a BE3 box its a BVM ML5T gearbox which by the look of the PR-net diagrams has a differant diff to the BE3 - The diagram shows a 'planet pinion spindle pin' which I assume has some function locating the spindle and as far as I can see appears to be held in position when the 2 halves of the diff housing are bolted together - I cant see how the pin can come out - but as I have never dismantled one I have probably completely misread the diagram. Has anyone taken one apart?

Thanks for the replies

Richard

citronut · Post by **citronut** » 07 Aug 2006, 22:38

i have had bits of the diff come through the gear box housing on a BX,i still managed to drive it home,but you could feel the diff was not working properly,also someone told me you are ment to put a shaft like a bit of broom handle into one of the drive shaft outlets int the diff if you are removeing both driveshafts to stop part of the diff droping,i dont do this and have never had a problem when refitting the driveshafts
regards malcolm

AndersDK · Post by **AndersDK** » 08 Aug 2006, 00:30

The earlier BE1 g/b's should have an axle stub inserted to avoid the diff gears collapsing. Not necessary on BE3 boxes.

This is the later type BE3 diff found in a DW10 (HDI) Xantia :
http://www.citroen-pr.net/catalogues/il ... 430050.gif

Note the absence of the old fashion lockpins for the gears and their spindle.
Its all about precision made parts which are held together smartly in the cage by help of special spacers. Also note the sun gears have a stepped lip/edge to keep the planet gears in position.

RStacey · Post by **RStacey** » 08 Aug 2006, 22:15

Thanks everyone but I've less idea about what the problem could be than when I started. I've still got the abnormal noise, and I'm due to drive the car to the south of France next week, so does anybody know if I can remove the diff to check it without removing the gearbox.

AndersDK · Post by **AndersDK** » 08 Aug 2006, 23:19

Removal of the diff in-situ depends on the free space to nearby subframe crossmember, steering rack etc. etc.
Drive axles must of course first be removed.

Before you get lost into this major operation -
Its not clear to me if you have backlash in all 3 situations :
1) RH wheel locked - LH wheel moved
2) LH wheel locked - RH wheel moved
3) Both wheels moved together ( car on wheels - rocked back and forth)

This is quite important to establish to avoid un-necessary dismantling & labour. I fear you could run into major problems aligning the diff unit with new clearance compensations etc. Hopefully some members have experience with the BE3 diff unit.

The differential unit is a halfshell housing added to the gearbox housing :
http://www.citroen-pr.net/catalogues/il ... 310060.gif

citronut · Post by **citronut** » 09 Aug 2006, 09:11

it would be quiker to just replace the hole gear boxes espcialy as you aint got much time,and i have never heard of anyone ever taking the diff appart with the gear box in place
regards macolm

jeremy · Post by **jeremy** » 09 Aug 2006, 09:35

I don't think diff gears are something for the faint hearted to take apart - or something that can be done in a hurry. My reasoning is that as has been said they are precision parts - and clearances may have to be established by shimming. This may not be the case and it may be for example that they are measured in the factory and the correct parts used.

They're all the same size aren't they? - not necessarily - the tool making them will wear during a shift - which means that somethings will be larger at the end of the shift and some may be smaller.

It was common practice to use selective aasembly for pistons and cylinders. Engines bored at the end of a shift have slightly smaller bores - whereas pistons produced at the same time will be larger. - Answer - use end of shift blocks with start of shift pistons. This is the reason in some workshop manuals 4 grades are quoted for components for nearly new engines.

To come back to the diff noise - if both tyres are the same size the diff gears are stationary with regard to each other when the car travels straight ahead - so cannot produce noise. Slight turn - slight movement - and I mean slight.

If the tyres are slightly different sizes the things go quiet on some slight corners of the right radius! - does work - found my Hillman Hunter had no axle oil this way many years ago!