Axle & Diff Upgrade
As rugged as the stock Defender is, when modifying it for heavier off-road use we needed to factor in the distinct possibility that it may end up carrying loads of a significant nature. This in itself puts additional stress on the drive train. But compounding this problem is the fact that we want to run larger diameter tires in order to help with ground clearance under the differentials. Using larger tires has the same effect on axles, differentials and drive shafts that a longer pry bar has when trying to shift a large rock with a lever. The further the force is from the centre of the arc, the more strain is exerted on the components. When this happens on a vehicle, failing to upgrade the strength of the drive train components can inevitably lead to a catastrophic failure that can strand the occupants out on a trail somewhere.
In addition to the strength upgrade, we also wanted to improve the off-road capability of the four wheel drive system. To do this we needed to add locking differentials. This allows us to lock the two wheels on each axle together, so if one wheel comes off the ground, the drive force will not be lost to the one that's still on the ground.
When it came to sourcing the right parts for this work, we didn't have to look very far. One of the largest manufacturers, if not the largest, is a company called ARB 4x4 Accessories. Based in Australia, they distribute their products all over the world. This made it very easy for us to get the locking differential components and accessories to replace the stock Land Rover differentials. The axles and drive shafts we bought from a company in Salt Lake City, Utah called Great Basin Rover, now known simply as GBR Inc.
You can look at the photos below individually with the descriptions, or open a "picture only" slideshow here.
Axle and Differential Upgrade Sequence
The axles we used to replace the stock Land Rover ones are bigger in diameter, and made with a stronger steel alloy. We also replaced the drive flanges on the end of the axles with more substantial ones.
We also had Great Basin Rover build us new differential assemblies using the ARB air lockers.
The front half shaft and CV joints were also replaced with stronger ones.
The red GBR drive shafts are significantly heavier than the Land Rover ones.
We also opted for double cardan universal joints on the drive shafts. The size upgrade is obvious.
Although this work is possible to do at home by a vehicle owner, doing it this way would be very difficult without a proper vehicle hoist. So we opted to have our local service shop do the work for us. Besides, the smell of gear oil is very unpleasant and toxic.
The various parts laid out on the floor ready for installation.
The rear differential housing all cleaned up and ready for the new differential assembly.
Ditto the front differential housing.
The outboard end of the axle housing, all cleaned up.
The finished wheel end with new drive flange and upgraded brake discs.
The finished rear drive train. We painted the components red to match the truck. The front looks much the same.