Simon's new Xantia V6 and Leaf blog

[xantia_v6]

I will take a wild guess, based on the evidence so far...

I think that the failure is due to one of the bolts holding the final gear to the differential cage coming loose and it has been hitting the gear on the intermediate shaft, gradually knocking chunks off of the bolt head. The angle of the gear teeth makes the gears move closer together or further apart, depending on the direction of torque.

[NewcastleFalcon]

Thanks for the extras Simon. The Micra's strut bolts/nuts were a grind off job for me, but I thought with a newer car like yours they wouldn't be too bad and they punch out with a bit of steel rod quite easily.

The job is making good solid progress, and of great interest.

REgards Neil

[Mandrake]

I will take a wild guess, based on the evidence so far...

I think that the failure is due to one of the bolts holding the final gear to the differential cage coming loose and it has been hitting the gear on the intermediate shaft, gradually knocking chunks off of the bolt head. The angle of the gear teeth makes the gears move closer together or further apart, depending on the direction of torque.

Interesting theory. I don't know enough about what a differential looks like to quite picture what you're saying though.

If this is indeed the failure mode, would you put it down to a factory assembly fault that has taken a few years to show up, or a design flaw etc... ? I can't think of any way that what you describe could be caused by owner driving style etc...

[RichardW]

One of these bolts:

If that is the case, (which would account for the once per wheel rev noise), then it's either a manufacturing or design fault (bolts not man enough, not tight enough, inadequate thread locking by design etc). If removal of the casing reveals that is the failure, then there might be a case for removing the lid from the new box and checking the bolts....

[mickthemaverick]

Having seen that photo I'd say that sounds like a good piece of deduction Mike! It would also raise the question of Nissan paying for the repair should it prove to be a loose bolt, cannot possibly blame that on the driver!!

[Mandrake]

One of these bolts:



If that is the case, (which would account for the once per wheel rev noise), then it's either a manufacturing or design fault (bolts not man enough, not tight enough, inadequate thread locking by design etc). If removal of the casing reveals that is the failure, then there might be a case for removing the lid from the new box and checking the bolts....

One of those bolts working loose until it touches the intermediate gear does certainly fit the symptoms. Are you thinking I should open the old box before fitting the new one ?

I'm reluctant to open the new one to be honest in case I have any issues getting it back together or it turns out there is a problem with it and I need to send it back.

I think the chance of a replacement having the same issue, if that's what it is, is extremely remote ?

[mickthemaverick]

I think the chance of a replacement having the same issue, if that's what it is, is extremely remote ?

This is a very tricky decision Simon, on the one hand if you open the old box and discover that the bolt is the problem and the only damage as such is to the bolt head, it begs the question: Should you replace the bolt, using appropriate locking adhesive and refit your original box and either return the replacement for refund, sell it on etc. OR fit the replacement box without checking if a similar occurence is going on OR remove the cover of the replacement box and check the bolts, if only for peace of mind? Hmmm.... if it were me I would either replace the bolt and resell the spare box or open the spare box and check it before fitting. Probably best to wait and see what you find as all this speculation may be completely pointless!!

[Mandrake]

In a surprise turn of events both the left and right seals (which are different sizes!) have arrived today from two different suppliers (Autodoc and Trodo) several days early!

So I now have multiple of both sizes of seal. This means I can fit the seals while the gearbox is still on the bench and proceed with the rest of the job over the next few days. (Although I've been informed that Saturday is a mandatory trip to the beach so I won't be working on it then! )

The only thing I don't have yet is new nuts/bolts for the bottom ball joint split on the hub - I ordered those via Nissan today but they don't keep them in stock (??) so won't have them for me until Monday. However I don't need those until the very end of the job - pretty much just before I'm ready to put the wheels on, so I can still do 95% of the work without them.

[Mandrake]

I think the chance of a replacement having the same issue, if that's what it is, is extremely remote ?

This is a very tricky decision Simon, on the one hand if you open the old box and discover that the bolt is the problem and the only damage as such is to the bolt head, it begs the question: Should you replace the bolt, using appropriate locking adhesive and refit your original box and either return the replacement for refund, sell it on etc. OR fit the replacement box without checking if a similar occurence is going on OR remove the cover of the replacement box and check the bolts, if only for peace of mind? Hmmm.... if it were me I would either replace the bolt and resell the spare box or open the spare box and check it before fitting. Probably best to wait and see what you find as all this speculation may be completely pointless!!

Maybe it will be the bolt, but that's just a guess at the moment. And even if it is, we don't know what other damage might have been done by chunks of bolt head being mashed between gear faces at high speed or getting stuck in tapered roller bearings etc.

I certainly wouldn't trust it without a very detailed inspection and testing of bearings etc, and none of the "experts" near me have wanted to look at a Leaf gearbox. As for returning the replacement one for a refund - it has a 2 month return period but that is for defects not if I just change my mind and decide I don't want it anymore.

[xantia_v6]

One of these bolts:



If that is the case, (which would account for the once per wheel rev noise), then it's either a manufacturing or design fault (bolts not man enough, not tight enough, inadequate thread locking by design etc). If removal of the casing reveals that is the failure, then there might be a case for removing the lid from the new box and checking the bolts....

Yes that is what I am predicting. Thanks for the illustration (I was a bit short of time to edit a photo).

My reason was that the debris are magnetic, and look like chippings rather than dust from grinding, so need to have come from a steel on steel percussive contact. I initially thought that a gear tooth may have become chipped or broken, but decided that would produce a different, and more consistent noise. It is still only a guess however.

[Mandrake]

Ok can someone confirm that I'm not going crazy and that there is a mistake in the Nissan service data...

I'm looking at the interface between gearbox and motor - as far as I can see there is a splined shaft sticking out of the motor and a splined hole in the gearbox with not much more to it than that. If so I'm finding the following text and diagram very confusing as I can't work out what the diagram is ??! Is that supposed to be a cutaway of the input spline in the gearbox ? Because if so the text doesn't make sense.

It refers to an o-ring etc however there is no such o-ring in the input shaft of the gearbox - here is a picture I just took and as can clearly be seen there is a spine part way down an otherwise hollow and empty shaft, and there is one external seal around the shaft itself:

There is no o-ring and no groove for one to go into, it's just a smooth shaft apart from the splined section. So what am I missing ?

[xantia_v6]

I think I saw on one of the yt videos that the O-ring sits in a groove on the motor shaft.

[Mandrake]

I think I saw on one of the yt videos that the ring suits in a groove on the motor shaft.

That would make more sense.

So is the diagram poorly drawn with the large white area below A actually the motor spline shaft and the dark area B to the right the void in the gearbox input shaft ??

And they're saying that as well as greasing the splines to inject 10-20g of grease into the void beyond the shaft ? Because if so the void in the gearbox shaft is clean and free of grease so unless someone washed it out thoroughly they didn't do that in the factory!

I don't have an o-ring or know a part number for one so I hope the old one will be ok...

If it just seals on the smooth section right at the entrance of the gearbox input shaft it shouldn't be too subject to damage on fitting.

[RichardW]

If I've done this right it should start at about 8:10 and he points to the O-ring

[xantia_v6]

In the diagram, the motor shaft is coming in from the left, and the left hand ball race shown is part of the motor.