Rear Corner Build – Part 1

Having rebuilt the prop shafts and installed new races and bearings into the hub carries, it is now time for an initial fitment of the rear end. The plan here is firstly to check that all the parts go together, but also to get an idea of how many spacers/shims are required to achieve the desired chamber angle.

Installing the Re-built Hub

I chose to start by installing the rear hub carrier onto the swing arm using the donor lower fulcrum shaft. As is suggested in the manual, it is certainly worth trial fitting the fulcrum shaft through the swing arm by itself, to ensure it fits and there isn’t a significant buildup of powder coat. For these swing arms, it’s true to say the shafts are a tight fit but there is no real excess of paint. With a thin coat of copper grease on the shaft to ease the installation and later removal, the hub carrier was then installed to the swing arm. This job is a little cumbersome as you have to hold the hub at the correct position whilst sliding the shaft through. Gentle taps with a rubber mallet and the job is soon complete. 

Installation of rear partly rebuilt hub onto the swing arm.

Installing the prop shaft

Next, the prop shaft is installed onto the differential. AK suggests that you begin by placing the donor prop shaft spacers between the prop shaft and differential. I can’t help but think this is a strange thing to assume as both the prop shaft and swing arm are new from AK, and so not sure how they can be sure these will be correct(ish). Since my original spacers were different sizes (6.4mm and 6.55mm thickness) I was extra careful to put them back on the correct side. These spacers slide over the bolts on the output of the diff. 

Donor spacers placed back on differential output flange.

The next step is to slide the prop shaft on and secure it in place with the 4 original 7/16" Unf Nyloc nuts. I decided here to add a washer between the nut and the prop shaft flange. The original nuts are used only during the trial fitting stage and will be replaced with new 7/16" Unf Nyloc nuts later when in final assembly. Whilst these nuts could be replaced with the somewhat more interesting Philidas nuts (part number NV607041#, which lead to an interesting morning read about these nuts), AK suggests the Nyloc nuts, so I’m sticking with their recommendation. 

Fitted prop shaft.

Fastening the nuts onto the prop shaft is a tricky process, as there is precious room between the opposing universal joint surfaces and unless you restrain the prop shaft, it will rotate as you tighten the nuts. After much trial and error, I found the easiest way to fastening each nut was it to rotate the prop shaft such that the 'target' nut was just off top center with the spline end of shaft resting on the floor. In this position, I could then use a 7/16’’ socket on a 100 mm extension to fasten the nuts. As you have to repeat this process for four bolts per side, this is certainly the least fun part of this job. 

Bring it all together

Now the splined end of the prop shaft can be passed through the respective rebuilt hub. To aid this, I slowly raised the hub/swing arm on the trolley jack whilst rotating and sliding in the splined end of the prop shaft. The tricky parts of this process are to protect the freshly painted hub carrier and getting the splined surfaces to line up. This is defiantly a cumbersome job where an extra hand would have been useful, but not essential. Once the prop shaft is slide into the hub, it is secured in place with a cone washer (smaller radius inboard) and a ‘special’ 1/16’’ nut (I found out why it is listed a 'special' in SNG manual later, no spoilers yet). Both these parts are taken from my donor car. The special nut is single use only, and so whilst I will use it for setting up the camber angle it will be replaced in final assembly. 

Prop shaft nut with cone spacer/washer.

With the hub installed onto the chassis for the first time, it is time to step back and admire the progress. If only I knew at that point that this would come apart so many more times. 

Hub fastened to prop shaft and swing arm. Resting on a trolley jack.

During my first attempt to fasten the special nut onto the chassis, I must have over tightened it (a good sign for later), as when I finally removed it, I noticed that inside the nut there is an inner coil/spring,  which is now unwinding itself from the nut. This must be another type of locking nut, and I guess what makes it ‘special’ and why it is single use…. 

Prop shaft nuts – over tightened.

Adjustment, Adjustments, Adjustments

With the rear corner assembled, the camber angle of the hub needs to be checked and altered. To do this, the top surface of the hub has to be 150 mm from the top of the chassis rail. This means careful raising of the hub on the trolley jack. I found the best way to measure the required distance was to use my father’s old set square, which luckily had a tongue length very close to 150 mm. I, therefore, placed the main surface on the chassis and raised the hub until it touched the set square. 

Set square used for checking the height. 

With the hub at the correct height, the aim is to ensure the (camber) angle hub is between 0 and 0.5 degrees (top of the slightly inboard) from the vertical. This angle of the hub is altered by changing the shims between the differential and the prop shaft. The concept being the thicker the shims, the more it pushes out the top of the hub. As with the front corner, I used an app on my phone to check the angle. For completeness, I used my spirit level, as, after all, I was going for near (or just off) vertical. 

On the off side, I found that with the original shim in place, the top of the hub was several degrees out beyond vertical. To resolve this, I took the entire assembly apart and reconstructed without the donor shim in place. This seemed to create almost the desired angle of 0.4deg.

The gap between the prop shaft and output flange

To verify the thickness of the desired spacer, again dismantled the corner and begun to fill it with 1 mm thick washers. The washers fitted nicely between the recessed region of the mounting plate and the bolts. I found these were a nice tool for experimenting with different shim thickness. Whilst I was not able to obtain the final shim thickness required, I was able to get a range of thickness in which I would find the desired angle. This should help determine how many shims I need to order from SNG. 

Differential output flange with washers to approximate the required shims.

Repeating the re-assembly process multiple times, with each time carefully checking the height of the hub, you can eventually get close to the correct angle.

Double checking the camber angle with a spirit level on the off side.

Final outcome

Having repeated this long process on both the off and near side, I ended up with an idea of what size shims I needed to purchase. 

• offside required no additional shims for spacing
• near side required between 5 mm and 6 mm of washers

Whilst I do not need any shims to get the correct camber angle, speaking with AK, they suggested filling the gap between the differential output plate and the prop shift with shims. I guess this is to spread the load onto the prop shaft, rather than relying on solely the pins. 

To achieve the required thickness on the near side, I might be able to get away with using the original donor shim. Whilst this might make things easy, I may consider buying some shims for this side so I have some flexibility when it comes to final fitment.

Now that I have an idea of what size shims I require there are several options to consider. 

• Speed sensor rotor (CAC8713) which has a 1 mm thickness for £13.99. The actual speed sensor part is not required for the AK build.
• A range of thicker spacers who’s part numbers are CBC4806xx, where the last two 'xx' are the thickness in mm, for example, the 5.5 mm spacer is part CBC480655. These parts varying costs but between £30 and £55, which are eye wateringly expensive for what they are.
• Rear Camber Shim 0.020’’ (or approx. 0.5mm in useful units)  is part number C16621# and are 50p each.

Based on the prices and a recommendation from AK, I decided to go for the rear camber shims. So I added an order for 16 to my growing SNG basket. This order will also include the rear hand brake shoes, which will allow me to finish the assemble to the rear hubs prior to the final rebuild of the rear.