I have witnessed the rear EAS of a seven seat DII fail catastrophically on an expedition - an air bag ripped from top to bottom and they could only limp on the bump stops between the camp sites on road, missing all the off road tracks through the mountains until repaired a few days later. They retro fitted HD coil springs to avoid any chances of a repeat and the other EAS equipped DII's owners spent the next fortnight crapping themselves they were next. I think EAS on an expedition vehicle is a very bad thing, and the trip leaders said they had seen six or seven such failures in the five years they had been running their trips, but had never seen a leaf or coil spring problem... These seven seat DIIs also have another complex suspension system up front called Active Cornering Enhancement, which is a hydraulically actuated anti-roll (sway) bar, which has its own compressors, reservoir, hydraulic lines and actuator. A full set of curly metal springs has got to be better in the middle of nowhere...
The TD5 engine also uses a dual mass flywheel and un-sprung clutch to make the engine run more smoothly. These are expensive, a ***** to fit in the field compared to sprung clutch plates with solid flywheels and much, much more prone to failure. LR provide a TD5 retrofit kit to convert the dual mass flywheel back to a simpler, more robust solid unit with conventional clutch plates.
While the Defender TD5 engine is pretty reliable, the Discovery version is more highly tuned and runs at higher boost pressure with longer peak boost times. This takes its toll on the head and manifolds, often warping both and shearing the manifold studs.
The DI uses easily replaceable wheel bearings and suspension bushes, but the DII's bearings are integral to the suspension components, so are not field replaceable unless you take large suspension components for each corner, rather than a small and cheap wheel bearing kit.
Then there's the engine management - a TD5 is ECU controlled, whereas a Tdi is mechanical (some later ones had a minor electronic bundle on the fuel pump associated with immobilisers and cruise control, but you could find a vehicle without one or retrofit a simpler injection pump. The EGR valve is also controled by a potentiometer on the injection pump, and that can be simply disconnected. So, make up a plug-in bypass connector to over-ride a failed alarm/immobiliser ECU and you have in a DI a vehicle that is no susceptible in any way to electronics failures...
Both use the R380 or ZF 4-speed coupled with the LT230, but the DII uses ETC brakes in place of the DI's centre diff lock. It doesn't perform as well, saps power when slipping and chews up your brakes. The DII LT230 can be made to have a locking diff, but I hear conflicting reports as to whether it's just the lever connections that are missing or the entire mechanism.
For all that, though, the DII body shells seem better constructed and are a bit more comfortable. I like the DII, well enough, especially the face-lifted 2003/4 model, but I'd get a good 300Tdi model every time.
