Whilst changing the axle spiders (inner CV joints) on my JTD115 this weekend I found that the diff axle (the 'pot' part where the spider slides into) had quite a lot of play in. Am I right in thinking there is a tapered bearing behind the oil seal which can be shimmed to take up the play, or is that just on the petrol engines?

If so, is it a case of just removing the diff shaft, prising out the oil seal and adding a thin shim to take out the play? Can it all be done in situ? I assume the shaft will slide straight back into the diff after?

How do you remove the diff shaft, does if just pull straight out? Any clips or anything holding it in? Obviously I'll need to remove the gb oil.

Also is there only one size of oil seal and shims? The spider I was sent for the drive shaft was too small for my shaft, (24 tooth spline instead of 26) and it appeared it would suit a smaller driveshaft, do I need to make sure the oil seal and shims suit the diameter of my driveshaft? (Are there 2 different diameter driveshafts?) I gather the OS and NS oil seals are different too, is that correct?

Is there anything else I need to change at the same time whilst doing this job? any other seals etc?

I really appreciate any help or advice anyone can give me with this. If there's a guide or photos of this procedure anywhere please direct me to it, I had a good look but couldn't find anything relating to the JTD diff specifically. Thanks very much.

What were you symptoms??? I am having a vibration under load and when I have a feel it feels like there is a little play in the diff bearing. so basically I want to know the exact same thing as you.

Yeah same thing really, vibration under load which is classic a inner CV symptom once worn. I eliminated all other possibilities first, but to be honest I could feel there was a small amount of play in the spider joint on one side anyway. So I went to change them both this last weekend and discovered there was also play in the diff axle bearing, this happened to be on the other side to the worn spider joint. Looking on ePER (and I'm no expert in using ePER) but I think they're tapered roller bearings, which I think I read somewhere can be shimmed? Im not sure if that's correct for the JTD diff, and was hoping someone here would shed some light for me. I'm not sure it the diff has to be removed or can it be done in situ. Any guidance much appreciated. Maybe its advisable to replace bearings with new rather then shimming the old one?

I would try a specialist or garage or even a gearbox rebuilder etc ?
I have only heard of reshimming being needed on either a diff rebuild or replacement, or a q2 or quaife diff being fitted, new bearings or new shaft may give different clearance between bearings.
as far as I know yes 2 taper roller bearings and shims are under a seal carrier.
but if its loose more likely worn bearings than requiring re shimming ?
these are general guides only to see what and how, different car different gearbox/diff.
but should help see whats involved
some pics in here
http://www.alfaowner.com/Forum/motoring-images/118596-q2-anti-roll-bar-guide-v6-gta.html
http://www.alfabb.com/bb/forums/164-168-1991-1995/153764-fitting-alfa-romeo-q2-differential.html
also try these guys
http://www.autolusso-bournemouth.co.uk/index.php?option=com_content&view=article&id=82&Itemid=204
they might talk you through whats acceptable play, can it be reshimmed tighter, can it be done on car etc more likely if you buy shims or bearings off them but worth a call.
bearings need pressing off on so definitely not on the car job.
probably best to have your reg and vin number handy .
ps looks like fiat want £50+ each bearing

sussexa said:

I would try a specialist or garage or even a gearbox rebuilder etc ?

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Thanks for all the advice sussexa, I was hoping to find some info or a guide about how to do the job myself. There's quite a bit on here about the petrol engine diffs, but not much about the JTD.

I've replaced both inner CV joints now and all vibration seems to have gone which is good, I'm just a little concerned about the amount of play in the axle coming out of the diff. I would have thought there should be no play here whatsoever, but there is a bit, I was quite surprised to find all the vibration had gone when driving. Maybe a bit of play here is ok, but to me it doesn't seem right.