Build 40. Differential

I was nervous about this job as most blogs report that it is a hard one to get in place as it is heavy and needs to be lifted from below. I decided I'd tackle it in two stages, the first getting it into place, prepped with pin punches, and then the second would be to fit the bolts and washers. I decided I'd leave the oil filling for after and complete that using a funnel and hose pipe.

Getting it in

Just as I did with the gearbox, I plan to use the motorbike jack, it is a stable platform and is perfect for the job. As before though it is not quite high enough when fully extended so this involved a bit of messing about to raise it onto higher wooden blocks. I utilised the sleepers I had knocking about for this and the engine hoist with a ratchet strap to just help with the small lifting (leaving the motorbike jack to do the heavy part)

I first inserted the pin punches to the lower boss join, then used the engine hoist to slightly raise the rear up and then used pin punches on the top boss joint. Once I was happy with this, I actually left it in place over the weekend as the weather went nice and sunny and I didn't want to waste the sunny weather being in the garage!

Securing the diff

Next was to secure the diff using the bolts and washers provided, I first got them all out of the fixing pack, noting that there are basically 3 different types of washers, all different thicknesses. The idea is that we need to pack out each side of the diff with washers to make it a nice tight fit (also don't forget the 4 schnorr washers that need to be used at the ends of each bolt).

For the lower bolts I ended up with one of the widest washers and two of the thinnest, I fixed them together with some copper slip, and coated the outside with some as well and then used a plastic shim to slot them into place, using a pin punch to guide them through the hole. It was fiddly but worked out in the end. Once one side was in and tightened I actually ended up adding another thin washer on the other side to pack the gap tight.


I did the same approach on the top, the bolt on the top needs tapping through with a rubber hammer as it is very tight, I made sure to really push the diff across once one set of washers was in, which again made enough space that I needed to pad out the other side with an extra thin washer.


All of this was then torqued to the required values (I think something like 81Nm and 47Nm, but double check with the manual, I'm writing this the day after I did it!)

Securing the prop shaft

Once the diff was secured, this was as easy as getting under the car and hand tightening the 4 bolts in place to bring the diff and prop shaft together in the correct place. I had to remove the grease nipple to allow access to the bolts with a torque wrench, so I used an 8mm socket to do this.

I then one by one removed each bolt, applied Loctite, and then hand tightened once more, before then locking them into place with the correct torques, The diff will rotate and fight against you here (provided you are in neutral gear) so the trick is to rotate the column with your hand (whilst the car is in neutral) so the bolt you want to tighten is at the bottom of the car, then put the gearbox into reverse. Go back under the car and tighten up to the 47Nm it recommends. Repeat with all 4 bolts (preferably do opposite bolts first), and then double check each bolt one more time to be sure after! Once this is done, I marked the bolts as torqued and moved on to the next step.

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