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Using all the good advice from this forum, I eventually have got round to changing the rear diff pinion oil seal - or rather have got halfway! Drained the oil, undid the prop shaft, got that flipping tight nut off and am now more than a little worried. The seal doesn't look anything like the replacement I have and certainly doesn't want to come out with my tentative levering BUT what really concerns me is the fact that the pinion has a huge amount of play side to side and up and down. Am I right in assuming there should be a bearing of some sort holding it in position in the nose of the diff and then the seal stops leaks going past it? Otherwise I can't see how it would ever hold oil as the shaft will never be in constant contact with the seal as it flaps around as the prop shaft does it's thing.

Any advice welcome.

:(

Malcolm

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Using all the good advice from this forum, I eventually have got round to changing the rear diff pinion oil seal - or rather have got halfway! Drained the oil, undid the prop shaft, got that flipping tight nut off and am now more than a little worried. The seal doesn't look anything like the replacement I have and certainly doesn't want to come out with my tentative levering BUT what really concerns me is the fact that the pinion has a huge amount of play side to side and up and down. Am I right in assuming there should be a bearing of some sort holding it in position in the nose of the diff and then the seal stops leaks going past it? Otherwise I can't see how it would ever hold oil as the shaft will never be in constant contact with the seal as it flaps around as the prop shaft does it's thing.

Any advice welcome.

:(

Malcolm

The lip of the seal fits on the outside of the diff pinion flange, which you have removed, this is what creates the oil tight seal. The flange, when it is tightened back up, also preloads the pinion bearing, that's why you have all the play now. The bearing will be visible once you get the seal out. Tentative levering probably won't shift it, you often have to use brute force and ignorance on them, :rolleyes: .Try the new seal on the pinion drive flange, it should be a nice interference fit. Also, if possible, measure the outside diameter of the new seal and the inside diameter of the pinion housing, a vernier caliper would be ideal for this but, failing that, you should get a pretty good idea with a ruler or tape measure.

HTH.

Mark

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Phew! So it doesn't sound as bad as I thought. I can certainly use plenty of ignorance (and a little brute force) to get the old seal out. I was going to measure/fit the new seal to the pinion before putting it in and although there is a slight groove in the pinion I think it will polish out. It was the excess play that had me worried but thank you Mark for explaining why I have it until the nut is tightened.

At least I know what to expect when I do the front one.

:)

Malcolm

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Phew! So it doesn't sound as bad as I thought. I can certainly use plenty of ignorance (and a little brute force) to get the old seal out. I was going to measure/fit the new seal to the pinion before putting it in and although there is a slight groove in the pinion I think it will polish out. It was the excess play that had me worried but thank you Mark for explaining why I have it until the nut is tightened.

At least I know what to expect when I do the front one.

:)

Malcolm

Hi Malcolm,

If you refit your new seal to a slightly different depth it will run on a new part of the Pinion Flange. If the groove in the pinion flange is only light, polishing it as you suggest will normally suffice to provide a good enough surface for the seal.

Good luck,

Mark.

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Screw a small self tapping screw into the old seal and prise it out with a claw hammer or a pair of pliers. When fitting the new seal use the old seal to knock it in, or a suitably sized socket. Old seal is more to hand though.

Mick.

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Hi mate,

Just rebuilt my diffs, I bought the centres from Steve at Crown Diffs http://www.crowndiffs.co.uk/ his site has good threads on building diffs very comprehensive and shows how he does it. When rebuilding mine he needed confirmation of the diff type as there are two different seals used and from memory they were significantly different.

Regards

Rob

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There are definitely 2 different pinion seals for the 300TDi..........experience tells me this!!!!! One is much deeper than the other. When you get the right one, make a note of which it is as you will need another one and it's nice to know rather than having to take it all apart to find out!!

To remove the old seal, I have a small two-armed puller that fits nicely under the old one with the centre shaft on the pinion.

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Thanks guys,

The suggestions are certainly appreciated.

If it still drips after polishing the small groove in the pinion and replacing the seal I will be back to square one, so whilst it's apart I may as well replace the old one and do it properly first time.

Malcolm

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was a month ago but

when i put a rear disco diff into the back of a mates 90 an changed the flange etc over the flange kit for it was if i remeber only 20-30quid so maybe worth changing the flange at the same time if theres a grove you also get a new nyloc nut to fix it

dave

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As Ibex94 recommended, I spoke to "crown diffs" - extremely knowledgeable and helpful. Not only are there different drive flanges (as they're called) but it depends what mud shield (the large washer thingy on the shaft) is fitted as to which oil seal should be fitted. One type of seal should even be fitted with a special tool. Luckily for me, mine is straightforward and he sorted out what I needed and it will be in the post tomorrow. Well impressed and will use them again. :D

Malcolm

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Eventually sorted! The old seal certainly put up a fight! It took hours to get the old one out and when I did, I found that whilst it looks the same as the replacement the whole of the outer part is actually metal. The only part that was plastic/rubber was the lip and the rest of it was just covered in plastic. If I ever have to replace this one at least it should be easier to get out (famous last words). As the front one isn't leaking at the moment I think I'll hang fire before replacing it.

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