Differential and Swingarm Install

Having earlier cleaned and painted the differential, the plan for this entry is to install this into the chassis. Once the differential is installed, the rear swing arms can be attached.

Installing the differential

Before installing the differential into the chassis, I first had to find all the required parts. This included the front pendulum, tie bar bracket and assorted nyloc nuts and washers supplied by AK. With these parts found, each bolt/shaft and bushing surface was given a healthy coating of copper grease. Then the cleaned and painted pendulum from the donor car is re-mated with differential. This slides over the differential nose and onto the large studs. 

Installing the differential into the car is certainly not a one-person task. I, therefore, enlisted the help of my better half and a trolley jack. The plan was to raise the differential using a trolley jacket, with one person to supporting and navigate the differential whilst the second person gently pushes the trolley jack and differential into place. Although this is certainly not an easy job, with a little care the differential soon slots into place.

There is then a range of nuts which need to be added to secure the differential in place. All the nuts shown below are provided within the AK kit. The back of the differential is secured with a pair of the M12 x 70 mm bolts, washers, and M12 nyloc nuts. AK also supply four 35mm x 14 mm washers, which are used as spaces between the rear of the differential and the chassis.

Rear ot differential secured to chassis, with spacers shown.

The two main differential bolts (which pass through the pendulum) require a 1”1/4 x 5/8” washer and an M16 nut. The differential nose is secured in place with 4x M10 nylocs.

Differential securely bolted in place.

Attaching the Tie Bar Bracket

With the differential secured in place, the rear swing arms can be a fastened onto it. This requires another rummage around the garage to find the relevant supplied AK and donor parts. With the exception of the swing arms, the majority of the components needed for this step come from the donor vehicle.

Parts required to install rear swing arm.

The swing arms attach to the pendulum (already installed between the differential and the chassis) and a rear tie bar bracket which fastens to the rear of the differential. To install the tie bar bracket, first slide the small right angle bracket (cleaned and painted from the donor car), and a pair of rubber domed washers onto the already cooper greased studs on the differential. 

Installed differential with exposed stubs.

Here I am using the rubber domed washers from the donor car. This is because after given them a good clean they appeared to in good condition. 

Right angle bracket and two of the doomed washers installed.

As well as applying copper grease to the studs, I also put grease on the inside of the tie bar bushes. With the troublesome memories of removing this from the donor vehicle still fresh in my mind, I am certainly going to apply extra copper grease here. Then the tie bar itself slides on and is secured in place with an additional set of dome rubber washers and M12 nuts. Whilst AK does not directly provide the nylocs for the tie bar, I seemed to have extra M12’s, so will use these when it comes to tightening things down.

Tie bar installed onto differential.

Now the swing arm is installed by passing the lower fulcrum shaft through from the tie bar, through two holes in the swing arm and finally through the pendulum. The fulcrum shaft is then secured in place with an M12 nyloc nut (according to AK). There are, of course, numerous washes and a protective metal tube placed in between. From rear to front, the fulcrum shaft should pass through the following: swing arm, tie bar, 2 washers, a protective tube, swing arm, 2 washers and finally the pendulum before being secured with a washer and nut. 

The washers which sits within this assembly are 1”1/2 x 7/8”. Annoyingly, these are not supplied by AK and given the lack of washers I found online, they don’t appear to be standard size. Since AK does supply the same size washers for the front lower fulcrum shaft (used in setting the chamber), I gave them a quick email to find out where they buy them from. The response was from Welland Engineering, but when I phoned up they seem to only really sell to manufactures with washers in boxes of 500, not ideal for my needs. The dimensions of these washers are not too dissimilar from the metric M22 washers and so I chose to use these instead. These can be ordered in packs of 10 from Amazon for very little money.

Missing Metal Tube

The protective metal tube (mentioned above) should have been supplied with the donor parts, but whilst this was originally part of the XJ40 chassis, through its life span the chassis was given continual ‘improvements’ which lead to this separate part being omitted in later models and changed for an integral part on later swing arms. Since my donor car was a later model, I do not have this separate part. The tube in question is part number CAC9384 and is advertised online for around £3, but no one seems to have any in stock (Bummer!). I then contacted Simply Performance who did have a few salvaged units lying around but by their own omission, they were not in great condition. However, Mark was able to get one posted to him so that we could measure its dimensions and investigate sourcing our own tube. Upon measuring Mark’s original tube, we obtained the following dimensions:

• Outer diameter: 28 mm
• Inner diameter: 21.2 mm
• Wall thickness: 3.4mm
• Length: 196.5mm

With these dimensions, I began searching online metal merchants. Matching the inner and outer diameters was not as straightforward as I had first hoped, as this doesn’t appear to be a standard size for stainless steel, even when its converted to the nearest imperial measurement of 1" x 14 SWG. I found these dimensions for plain steel but I didn't want to buy this as I would have to paint the internal surfaces to avoid them rusting.

The closest match for the radial dimensions I found was 25 mm outer diameter with a 1.5 mm wall thickness (22 mm ID). Whilst most major online metal stockiest had this in stock and would cut the tubes down to length, they generally had very high shipping fee (£30+). A better option was to order a 1 m section of this tubing from eBay, which cost £13 including p&p. I would have to cut this tube down to length, but I could make two new sets of tubes for both mine and Mark’s cars easily. Ordering this tube was a no brainer and it arrived within a few days. 

Tube section on workbench ready to cut down to size.

Despite having the dimensions of the tube above I did check the oversized diameter and length of the tube against my actual chassis.

Comparison of fulcrum shaft and purchased metal tube.

Having offered up the freshly cut tube to the temporarily assembled swing arm, I could check its length and trim it down with the grinder. After all, was said and done, the actual dimension of the tube matched Mark’s original measurements very closely. 

Offering up the cut tube to the gap between the swing arm.

Two spacer tubes down to size. I also made an extra set for Mark.

Assemble of the Swing Arm

With the protective tubes cut to length, it was the normal process of taking everything apart (again) to then re-assemble it with the new tube. The final layout of parts is now shown in the image below. For final assembly, it is important to ensure that all metal to metal surfaces (washer to washer included) are given a liberal coat of copper grease. When it came to fastening the nut at the end of the fulcrum shaft, it appears that AK’s statement of it being an M12 nut, is wrong (at least for my vehicle). Luckily, I still had my donor nut safely stored away and so with a coating of POR15, this was pressganged back into service. I will have to add some lock tight to it as well. 

Final layout of parts used to install a swing arm.

Fulcrum shaft going into tie bar

Close up of swing arm with the protective tube.

Installed swing arm with the metal tube.

With the process repeated, the second swing arm is installed. 

Both Swing arms installed.

Now that the swing arms are installed, the next step is to build up the half shafts and rear hubs. These separate items will be the focus of the next posts, before returning to installing them on the chassis.