Rear Axle - Jag Rear Overhaul - Part 6

Can you believe it, I am finally getting some shed time again. We have had a really busy life in the past 12 months with major home renovations and repairs. It sapped all our money and our time too. In fact it is still going on but is coming close to an end.

In addition to that I went mad and got involved in road cycling. That takes a bit of time too but I am much better for it, having lost a heap of weight and getting some really good health results too...... actually that was until boxing day! Yes my blood results and reduced need for medicines is all good, but I thought I'd have a crack at mountain biking while on holiday and I came off. In the process I developed another health condition! I smashed my collar bone....no not just a break I smashed it! I am suffering for it still and can't lift a whole lot which again has impacted on shed time. Coming right now though....oh and the internet shopping and parts collection activities have been carrying on so there has been a bit of prep work going on in the background.

Anyway....today I got back onto the Jag rear, namely the diff head. In my last post about the diff I was sanding and painting the head. To date I have spent 45hrs doing that. Fingers have been blistered cracked and bleeding, but it does look pretty good so far.

Before sending the head away with all the new bearings, seals, an appropriate gear set and a limited slip unit, I painted the head in lacquer as this will be a base colour for the silver top coat but it also means the porous primer is protected from the oil and grease during the assembly process.

Its not easy assembling a jag diff and getting all the clearances right so I had to take it in to Diffs R Us to be rebuilt. Even then it cost an arm and a leg as it took him 13hrs to set that up and assemble the hubs. Don't try that at home!

So here it is in all its glory!

It looks pretty good all assembled with the polished brake mounts in place too. The claws out the front will hold the handbrake calipers.

Notice the countersunk screws that hold the shiny mount plate in place. These will soon be a cause for concern!

Once the brake discs go on I won't be able to put a bolt through the brake mounting plate and through the caliper itself, in the next pic you can see the hole is partially obscured here by the edge of the disc. So to overcome that I will need to put the bolts in before putting the disk on. That is a problem too though as I can't slide the calipers on while the disc is in place. Its okay though as the calipers are a 2 piece unit I will be able to split them. Bolt one side on to the mounting plate, then slip the disk on and lastly put the other half of the caliper on.

It means it will be a pain in the backside if I ever need to remove the disc as I will need to split the caliper and bleed the brakes when I reassemble, but that is probably not going to happen very often (if ever) as the back brakes don't do a heap of work and the car wont do too many miles.

Replacing brake pads will still be easy as they come out through a slot in the back.

In this next pic you can see what it will look like once the caliper is mounted. See how it grips around the disc. This is why I can't mount the caliper then put the disc on later. If you look carefully you can see a join down the centre of the caliper where the two halves come apart. That big rectangular opening in the back face is where the brake pads can be removed and replaced.

Here is a side view with the caliper not quite in position so you can see the mount holes.

Actually thats not quite true....its because the caliper wont quite fit yet. The caliper mounting points are about 2 mm too thick so the caliper would be sitting off centre if I plowed ahead now. That would not be ideal!

You can see in this next pic how the mounting lug on the caliper overlaps the mounting plate. Its only 2mm but enough to screw things up. I will get that 2mm machined off, then we will be good to go.

As you saw earlier the mount plate runs pretty close to the brake disc so there is no room to get a bolt head down in there, so I need to use these countersunk bolts. Once I countersink the holes they will sit down almost flush with the mounting plate. Here it is before.....

....and after.....

When I bolt the caliper on I will use spring washers and a locking nut so that there is no chance of this bolt coming loose and fouling the brake disc. It wouldn't be the end of the world if it did....it would just scrape on and probably damage the disc and it would make a horrible noise.

Remember though how I said earlier that I was concerned about the countersunk screws that hold the shiny mount plate in place. While these are countersunk and out of the way, they would be a real problem if one came loose. If you look closely in this next picture you can see the studs that go through the drive flange have a head on them (see the reflection in the shiny brake mount plate) and whats more they are directly in line the countersunk brake mounting plate screws. If one of those countersunk screws came loose it would hit the drive flange stud and stop that axle turning....now imagine what would happen if that occurred at 100kph. One rear wheel locking like that would be catastrophic!

I looked at the other jag diff I have here (now remember these don't have the same clearance issues as they don't use a shiny brake mount plate like I have made for the Wilwood calipers) and I remember now....the original bolts at that point are held in place with locking tabs.

Sooooo, back to the drawing board.

I don't feel I can effectively lock the countersunk screws so I will go for a traditional bolt and use a spring washer under them. I will also drill tiny holes through the heads of the bolts and wire them together. This is overkill but I want to be really certain about this.

Here are some sample pics off the web showing the bolts with their drilled heads and below that a pic of what they look like once wired up.

Another modification will be required though as I don't have room for a bolt head and a spring washer in between the brake mount plate and the flange studs, so I will need to recess them into the brake mount plate. All will be good, just more machining and more bolts required.

Lastly, here is the head all mounted up on a stand ready for me to apply paint.

Next time we should see paint and be able to put the unit back together again!