Replacing the diff pinion oil seal.

[Mr Ian]

Hi Les, good write up, just a point though. Looks like someone has incorrectly matched the seal and cover. There are two types of dust/dirt cover. Early flat type with a conventional seal and the later dished type for use with the seal you fitted. If you want the later seal you should also use the later cover. Regards. Ian Ashcroft

[CwazyWabbit]

Help!:/ I decided to have a go at this job myself after reading this helpful post! Long story short......I took off the propshaft expecting to see a castellated nut or nyloc nut and I am greeted with a 15mm bolt! I take all the necessary measurements etc and undo the bolt! The flange comes out and the seal looks nothing like frc8220 or frc4586! Can anyone shed any light in this?! Do I have a completely different diff assembly?! Thanks!

Stick a few pictures up and I'm sure someone will recognise it.

[zardos]

Help!:/ I decided to have a go at this job myself after reading this helpful post! Long story short......I took off the propshaft expecting to see a castellated nut or nyloc nut and I am greeted with a 15mm bolt! I take all the necessary measurements etc and undo the bolt! The flange comes out and the seal looks nothing like frc8220 or frc4586! Can anyone shed any light in this?! Do I have a completely different diff assembly?! Thanks!

This is probably a disco diff with a 3 blot flange to connect it to the rubber doughnut, instead of the 4 blot flange for a UJ connection

See

[Arleshhh]

Thanks for the help guys! I think I may have a Discovery diff assembly but with a defender 4bolt flange fitted! The seal looks like FTC5258 which is for the Discovery! Just wondering did Landrover have a kind of cross over period where they may have used the same diffs in both Defenders and Discoveries or do you think mine may have been swapped at some point!?! Ill try taking pictures when I come to do it! Had to put it all back together without new seal because I had the wrong ones!

[lusso]

Les,

Thank you for this informative tech article. I replaced my pinion seal using your article. It went very smooth, with the exception of how cold it was yesterday. I learned a valuable lesson: wind and gear oil equal a huge mess.

Cheers

David

[Suffolk Defender]

Hi all, i am looking to follow this post to replace the pinion on my rear diff.

Its not clear to me how i know which rear axle i have, Rover or Salisbury? i think its the Salisbury. how  do i know for sure?

I assume once i know this i can get the right seal ordered.

 

Melv

[Davo]

Easy! The Salisbury has a plate bolted onto the rear of the axle housing, whereas the Rover type doesn't. A quick image search will show you what I mean. 

[CwazyWabbit]

[Snagger]

The procedure for doing the Salisbury diffs is the same.  The flange nut is peened rather than nylock or split pinned.  There is a lot of concern over the bearing preload because of the fact that while the Rover diff's bearing preload is set by shims and won't be affected by overtightening the nut, the Slaisbury preload is set by the torque on the nut - the tighter it is turned, the tighter the preload.  It actually works by crushing a special tube between the bearings, which takes about 250'lbs to start crushing and takes more and more torque to further crush as the bearings close on each other.  So, while the ideal thing to do is mark the pinion end and the nut with alignment marks, if you forget, tightening to a maximum of 250'lbs will not apply excessive preload and will also not lead to a loose pinion.  You need a very hefty torque wrench to get close to those levels and will struggle with a 3' breaker bar with the vehicle on a ramp.  The worry about the correct preload is entirely academic.

There is a lot of fear about working on Salisbury diffs, but in practice, it's unfounded.

[Maverik]

6 hours ago, Snagger said:

There is a lot of fear about working on Salisbury diffs, but in practice, it's unfounded.

To digress, I don't think its fear, more just the shear difficulty in buying/fabricating a diff case squashing tool puts folk off, that and the fact that if you get the simple squashing of the case wrong you can over stress the case... which reminds me I've got a spare one lying around, I might try make a tool for it...

[Suffolk Defender]

ah thanks for the responses! i have a salisbury on the rear and the front is the rover.

7 hours ago, Snagger said:

The procedure for doing the Salisbury diffs is the same.  The flange nut is peened rather than nylock or split pinned.  There is a lot of concern over the bearing preload because of the fact that while the Rover diff's bearing preload is set by shims and won't be affected by overtightening the nut, the Slaisbury preload is set by the torque on the nut - the tighter it is turned, the tighter the preload.  It actually works by crushing a special tube between the bearings, which takes about 250'lbs to start crushing and takes more and more torque to further crush as the bearings close on each other.  So, while the ideal thing to do is mark the pinion end and the nut with alignment marks, if you forget, tightening to a maximum of 250'lbs will not apply excessive preload and will also not lead to a loose pinion.  You need a very hefty torque wrench to get close to those levels and will struggle with a 3' breaker bar with the vehicle on a ramp.  The worry about the correct preload is entirely academic.

There is a lot of fear about working on Salisbury diffs, but in practice, it's unfounded.

Very useful to know, thank you for sharing this as this was the part of the procedure i was not sure about. 

So how does one know how much toque that nut needs then? is it standard per vehicle?

I was also told that the prop shaft nuts need replacing when removed, is this true?

[Les Henson]

Before undoing the nut. make a mark on it and make a corresponding mark on the thread. Count the turns to remove the nut from the thread and do the opposite on reassembly. That way there will be no difference between the tightness prior to disassembly and assembly, so if you had other problems, that will be there. Replacing the flange nuts/bolts rather depends on the condition of the old ones. Some people replace them every time they have to be removed and others if they think they need it.

 

 

 

Les

[Snagger]

As per my first post and Les' post above, mark the flange nut and pinion so that you can tighten the nut to the same position on reassembly.  But it's not that important - the torque needed to increase the preload over what has already been set is enormous, so you won't overtighten it without  damned big breaker bar and a pinion flange locking tool.  I have done this a couple of times on ratio swaps (4.71-3.54) where I moved the pinion and carrier assembly from one axle to another and tightened the nut to 150'lbs, enough that there is no play but nowhere near enough to change preloads, and it worked perfectly.  You also don't need spreaders to get the diff centre out with pry bars; it just makes it considerably easier.