Moving on from the previous post about the front axle, we arrive here, at the rear axle as promised.

Again, as with the front axle, I had to remove all the braking and suspension components. This obviously includes the spring platforms, dampers, brake calipers and the A-frame. All the bolts were rusty as with the front axle. However, this time I was prepared. I used a combination of 1600 Celsius blow torch, and –40 Celsius freezer spray. It really made (almost) everything easy to undo, I did have to use a few other techniques to remove some things. But for the most part the fire/ freeze method worked.

So onto the axle.

You can see clearly how the rear brakes are connected, a simple T piece. This means that the Disco’ doesn’t brake opposite corners as with most other cars. It has individual circuits for the front wheels and a single circuit for the rears. This means should the worst come to the worst and the rear line breaks somewhere ahead of the T piece, you lose all rear braking. However the handbrake could be used instead. Although, saying that, there is only one master cylinder. That means all fluid has one original pressure source, which means the car only really has a single circuit.

Below are a couple of pictures after I removed the dampers, spring platforms and brake calipers. I removed the dampers using a nut splitter, as you can see one of them is a bit bent.

The only thing left to remove was the A-frame, which is obscured by the axle as it was upside down when the picture was taken.

The A-frame is connected to the axle by a ball joint, which is secured by a 30mm king nut and split pin, oh joy! All the fun of a rusted split pin in a very confined space, super! I took the easy route and just cut it off and used a nail punch to remove the legs. Now for the nut, because it was in such a confined space, the only thing I could fit on it was a 30mm spanner. This meant I couldn’t get enough torque on the nut to undo it.

So, I drilled the edge of the nut and used a chisel to split the nut, after which it came out by hand.

As an aside here is the seized bush, it is ruined. The inner metal ring of the bush had rusted to the bolt rendering the bolt immobile. This meant I would not have been able to remove the A-frame from the chassis without cutting the bolt. I won’t be able to remove the bush without a hydraulic press, unless I drill a large hole through the bolt.

Below is a picture of the axle after I removed all the external parts.

So now is the part of the walkthrough that is  important.

Pre-preparation: Drain the axle of its oil. As before note the colour of the oil. There is a chance that if you do any off-roading, in deep water particularly, the oil will be water contaminated. It will be white and a bit frothy, or if the oil has been contaminated for a long time will be mixed with rust, and be rust coloured and frothy. This is the reason you should check the colour of your diff oil after every deep water session. As it happens, the colour of my oil was a deep black, indicating it was time for a change anyway. There were no silver particles either so, I’m fairly happy.

Step 1: undo the 17mm axle bolts (5x).

Step 2: pull the axle shaft out from the axle.

Step 3: bend the locking tab away from the 52mm locking nut and remove both.

Step 3: remove the 52mm hub adjusting nut and spacer.

This reveals one of the two wheel bearings behind the hub. As you can see the grease has seen a lot of mileage, it is contaminated and there also isn’t much left in there either. At the very least it requires a re-grease.

Step 4: pull the hub from the stub axle. In the picture below you can see where the bearing sat on the stub axle.

Step 5: put an oil receptacle under the stub axle. Undo the 17mm stub axle bolts (6x).

Step 6: remove the stub axle.

Repeat for the other side.

Step 7: undo the 15mm final drive housing nuts (10x), and remove the final drive unit in the same way as the front axle.

Finally, wrap up the open ends of the axle and put it away ready for sand blasting. This rear axle is in a worse state than the front axle, mostly because the front axle is sat under the engine, and this being a rover engine has a few leaky bits. But in all honesty, it isn’t really that bad.

Not like the spare axle casing which is toast. There are more than a few holes in it.

At this point, I thought it would be interesting to show you my brake calipers. On the front, they are 4 piston calipers, and on the rear they are 2 piston calipers. They are surprisingly high spec for your average road car, which tend to have sliding calipers. You would tend to find similar calipers on fairly sporty cars, such as a Porsche Boxster. They were manufactured by AP Lockheed a.k.a. AP Racing. They have 4 quite large pistons, which means a large, fairly uniform contact area on the pads. Which in turn means the pad is pressed more evenly onto the disc (than a single piston caliper, which will tend to bend the pad slightly), which mean a greater area of the pad is used against the disc and results in a larger stopping force for the same pedal input (with everything else being assumed to be equal). Having multiple opposed piston calipers allows for larger brake pads as well, which means heat is dissipated more quickly (as a larger surface area can absorb/ dissipate more heat than a smaller one). This results in a braking system that is more resistant to brake fade over a series of heavy braking situations than a sliding caliper (in general). Which is a plus on the Disco’, as the discs are not ventilated.

These brakes are good, but not the best. They are bolted together rather than being mono-block. So when I brake (simplifying the problem down by ignoring all material deformation, mechanical or thermodynamic, heat transfer and friction, and assuming a completely incompressible hydraulic fluid), the pistons press the pads onto the disc, which exerts an equal and opposite force on the pistons. This equal and opposite force will try and force the caliper apart, which is prevented from happening by the caliper bolts. Caliper bolts will not be as good as taking the load as a much larger cross-section of uniform material, as in a mono-block caliper. In the real world, the bolts are a source of loss of efficiency of the calipers.

However good/ not good calipers are theoretically, it doesn’t change the fact that my calipers don’t actually work. At least not as they should, some of the pistons are seized. They could do with a rebuild, which is what I am going to do. Probably new pistons (dependent on condition), new seals and new bolts (maybe), as well as a de-rust and fresh coat of heat resistant paint. Ideally, I would like them as new, we’ll see how long my patience holds up whilst doing this, I have 8 to do. As long as I end up with a working set I won’t be too unhappy.

Anyway, that is it for another edition. I have lots to be getting on with, like removing thousands of bushes, sand-blasting lots of things and rebuilding these calipers (and eventually axles). Cheerio.

So, it has been a while since my last update, it is practically Christmas. I have been busy stripping and cataloguing all four of my axles. I have decided to make this a little bit of a walkthrough, that way it is very obvious, when I get back round to rebuilding them, where everything goes. As a result, I will write about the front and rear axles separately as there are a lot of pictures. I apologise if it’s a bit tedious, but stick with me.

The first port of call is to strip the axle of its suspension and braking components. It basically took me a whole day to get everything off. For a start, the last person to put the wheels on had done up the wheel nuts so tight, I couldn’t remove them with an impact gun. I only just managed to remove them with a 60cm breaker bar whilst jumping on it. Now I weigh about 100kg, so that puts the tightening torque at roughly 590Nm or in other words more torque than a 2005 BMW M6 produces (520Nm). That sort of set the tone for the rest of the day really. Frustrating didn’t really cover it. The damper nuts were badly corroded, and I broke my 8mm spanner trying to stop them spinning. In the end I used an old fabric oil filter remover and a 1600degree flame (not ideal on something that can burst/ explode if too much pressure builds up) to remove the securing nuts (I couldn’t get a nut splitter onto them). The steering damper was much the same. The track rod ends were corroded, and getting corroded split pins out from between the crenellations is no fun, so I just cut them off, then used a long breaker bar to twist the nuts off. When it came to brake calipers, clearly the same person who tightened the wheel nuts tightened the calipers up. It took two people to undo the calipers, one to hold the axle still with a wrecking bar, whilst the other jumped up and down on a breaker bar.

Anyway, that’s the whining over and done with. I did eventually get everything off and put into the barn, where I will rebuild/repaint/throw away (delete as appropriate). So here we go with the main point of the post.

Pre-preparation, drain the axle of its oil. Whilst it is draining take note of the colour of the oil, mine was thick blue/black and had some lumps in it. Importantly there were no silver shavings/particles coming out. Indicating before I have even dismantled anything that the internal oil seals are dead and the diff oil has mixed with the swivel grease, but the gears should be in good nick. The actual colour is somewhere between golden syrup and black treacle.

Step 1: remove the rubber dust cap on the end of the axle shaft.

This reveals a cir-clip and several shims (VERY important not to lose those) which control/ set the end float on the axle shaft.

Step 2: remove the cir-clip using either: cir-clip pliers (easy) or needle nose pliers (hard) and some sort of lever. Remove the shims (3x)

Step 3: undo the 17mm drive flange bolts (5x).

As you can see, the drive flange is splined to the axle shaft, and is bolted to the hub. This obviously is then connects to the wheel. I.e.: axle turns drive flange, drive flange turns hub, hub turns wheel, wheel moves car.

Step 4: bend the locking tab away from the locking nut. Undo the 52mm locking nut and remove.

Step 5: undo the hub adjusting nut. This nut adjust the pre-load on the wheel bearings. Too tight the wheel bearings heat up, lose lubrication, wear quickly and fail. Too loose the hub can move around (Goldilocks springs to mind) the wheel bearings will take non-uniform loads, and may fail.

Step 6: remove the hub and brake disc assembly from the stub axle.

Step 7: place an oil receptacle under the swivel housing. Undo the the 17mm stub axle bolts (6x).

This reveals the axle shaft.

Step 8: straighten the swivel housing. Remove the shaft. Also remove the paper gasket from the mating face.

Lather, rinse, repeat for the other side.

Step 9: undo and remove the 15mm final drive housing nuts (10x).

Step 10: using a hammer and a block of wood, hit the housing in various directions to split the casings.

Step 11: use a soft, flat bladed tool to work the housing down the studs. Remove housing using care, it is the heaviest part of the axle weighing in at somewhere between 30 and 40kg (estimated).

This reveals the differential, crown wheel it’s driving pinion. I have to admit, it is quite a beautiful piece of work.

Step 12: turn the swivel pin housing onto the lock stop, undo the 8mm bolts holding the oil seal retaining plate and washer.

Step 13: remove the oil seal.

Step 14: on top of the swivel pin housing, remove the top swivel pin by removing the 17mm securing bolts (2x). Take care not to lose any shims (3x).

Step 15: remove the swivel housing. Lift the swivel housing up and then rotate the top of the housing towards the ground.

Again lather, rinse repeat for the other side.

At this point, we can check the state of our swivels thoroughly. As you can see from the below picture mine are toast. The picture immediately below is the drivers side bearing housing. Stones have chipped away the chrome finish, this has allowed rust to form on the un-protected steel underneath, which then undercuts the chrome coating which then cracks off. Vicious circle.

The passenger side is worse (below). This has a knock on effect of shredding the edges of the oil seal.

The results of which can be seen below. This is the passenger side swivel pin housing. You can see the colour, immediately indicative of rust mixed with what little grease there was left in the housing. The top bearing (left in the picture) has either corroded and destroyed itself, or seized and been destroyed when I started moving it.

Here is what I scavenged from the swivel pin housing. A bearing cage, but not a complete complement of rollers. We are about four short, goodness only knows where they have gone.

In any case, it doesn’t matter, I cannot re-use that and nor would I want to.

Returning to the problem at hand, I had to remove the swivel bearing housing. The problem with these is that they are a double hex 14mm bolt, or at least were, mine were corroded and some were rounded (they were around 13.5mm there isn’t even an imperial size that fits). Additionally, there isn’t enough room to use a socket and ratchet. So, I used my most favourite of implements, an angle grinder. You can see the results below.

I trimmed the heads off, and then set about regrinding the studs to roughly hexagonal. My plan was to use a rounded nut removal socket. But I got over zealous with the angle grinder and started to gouge the mating faces.

Not great work. I may be able to save the axle casing if I shave a millimetre or two from the case and then make a shim using a paper gasket between each mating face. Other wise this will probably be a permanently leaking axle. Basically I am saying don’t do this if you can avoid it.

It is at this point I should also say that this is my spare axle. This axle came from the frame I took to Tomcat Motorsport, a 1993 300TDI. It has had an extra 5 years (or so) of grief compared to my V8 Disco’, so everything was that much more corroded and more difficult to remove.

So I guess I have been caught out. The above walkthrough is from my spare axle (barring the first picture and paragraph). I guess I should add some small print that says enhanced in post production or something of that ilk. The dis-assembly of my V8 Disco’ axles went off without a hitch (well apart from the first paragraph). I removed the swivel bearing housing using a 14mm spanner and a 5lb lump hammer. Both swivel bearing housings are Teflon coated, so no rust on them. However the passenger side swivel was leaking quite badly. It also looks as though someone tightened up the hub nuts too much and the wheel bearings over heated, the grease was like earwax. This was  perhaps to hide the fact that they wheel bearings were knackered, either way it it was the cause or effect of knackered wheel bearings. Anyway, the axle casing is now waiting for sand blasting and re-painting. I am going to be putting fresh bearings and seals throughout so I effectively have a brand new axle.

The next update will contain a walkthrough of the rear axle. This will be very much shorter, as there is a lot less to it. Until next time.