I recently replaced the rear diff deal on my SWB with the standard double lip seal, it failed after 50 miles, even though it was exactly the same as the seal I replaced which had developed a small leak. I also replaced the Pinion drive flange, as that was pitted and fitted a new mud slinger. All new parts with correct part numbers from Britpart (made in India). When I looked at the failed new seal it had been crushed and the outer seal torn away by the mudslinger, a puzzle as all parts were replaced like for like. I have read alot on this forum about failed seals but no one seems to mention the diff pinion spacer part no 539745 which has the effect, if fitted, of moving the pinion drive flange and mud slinger further away from the seal. Some diagrams show this some do not for Series 3, some show it for the Defender. I think it is missing from my Series 3, but bit of a mystery why all was fine previously, unless it was there and has broken and fallen in the diff, and if fitted will it allow the split pin to be fitted through the castellated nut as with the spacer the nut will not be tighten as far down the pinion thread.

Any thoughts?

The spacer doesn't change the final position of the pinion as it is a collapsible spacer.

The pinion nut is tightened until there is the correct preload across the bearings, and the location of the bearings themselves determines the position of the pinion.

All the collapsible spacer does is to increase the clamping load between the pinion nut and the drive flange, stopping the pinion flange wiggling around across the clearance in the splines under changes in torque.

As the spacer collapses during tightening of the pinion nut, ideally, you should replace the spacer every time the pinion nut is disturbed.

Thank you for your reply. The collapsible spacer is fitted to the Salisbury Diff fitted to some Series 3's, part no 607197 and is replaced every time the pinion flange is removed as you correctly say. My thread refers to the Rover Diff which has or not sas the case mybe a solid spacer part no 539745, as shown on the attached, and so would effect the final position of the pinion flange and mudslinger.. I was looking for people's experience with this type of diff.

When you fitted the seal was it set proud of diff casing or inside it, I’ve not been further than replacing seals and flanges on mine

The first seal was a double lip seal so it was set correctly proud of the diff casing, and I believe was crushed when in use because of the lack of the spacer. I have subseuently fitted a single lip Corteco seal which seams better quality than the double lip, and this sits flush with the diff casing and there is just enough clearance by the mudslinger when all is tightened up with no spacer fitted. When I get a spacer I am going to dismantle everything again fit the spacer and see what the claerances are like.

IGF said:

Thank you for your reply. The collapsible spacer is fitted to the Salisbury Diff fitted to some Series 3's, part no 607197 and is replaced every time the pinion flange is removed as you correctly say. My thread refers to the Rover Diff which has or not sas the case mybe a solid spacer part no 539745, as shown on the attached, and so would effect the final position of the pinion flange and mudslinger.. I was looking for people's experience with this type of diff.

Click to expand...

Sorry, yes, you are quite right.

Steve2286w thinking about your question has helped me solve this problem and watching a few Youtube videos on upgrading Discovery Pinion Flanges to give 4 bolt fixings for the prop shaft. Firstly your point about setting the seal, I did not realise the double lip seal should be driven into the diff housing until it stops against the recess lip. I thought because it had a slight edge to the outside of the seal , that this edge should stop flush with the diffcasing, my mistake. So now I know all seals single or double lipped should be fully recessed into the diff housing.

So to the spacer. Compring diff pinions some are multi spline and some have 4 large splines. It looks to me like the multi spline diff pinions are shorter that the 4 spline ones and so require the spacer, that accounts for the reason why my Landy does not have a spacer, it has the 4 spline diff pinion. Mystery solved. I will take it all to bits again and check this out.

Thank you for your thought provoking input.

good one, dont forget to clear the axle breathers which can force oil past seals if they pressurise