For the youngsters:
I used to live in Weipa, where I owned a 85 4wd L sedan, and then did a Suba club trip in 99. The conditions may have changed a little since then, but I doubt it as the main reason for the road (the mine at Weipa) has scaled back since then.
Vehicle prep:
- Get your cooling system sorted. If you have a suspiscion(?) your radiator could have a problem get it checked out. If it fails, its 1000km to the nearest shop & I got caught in a vehicle that couldn't do more than 80 even with the heater on full tilt. This meant leaving an hour before everyone else in the morning, stopping for a 5min lunch when everyone caught up (while they stopped for an hour) & then an extra hour in the evening catching up. Not pleasant.
- trailers are a definite no no. The roads are badly corregated & the trailer will quite literally get shaken to bits. The roads up there are littered with their remains
- expensive all terrain tyres are not necessary. some decent road tyres with wide grooves (Kumhos are good for this) will be sufficient. Most of the gravel is just loose. They will cop a hammering though, so if they're borderline, replace before leaving, because there's no availability.
- shocks & springs: find some old almost worn out ones to have fitted. Do not get you beaut new ones unless the are soft. The roads are heavily corregated, you need to be able to accelerate past the "shaking part" until you are "gliding" over the top of them. The softer the suspension, the better
- no double shocks: the brackets for these will be broken & they'll become useless. I think on the club trip I did up there every single double shock got broken or removed
- lift kit is basically a must, or else good ground clearance, or a lack of care of your undercarriage. I was in an unlifted wagon for the trip.
- normal fuel isn't really that much of a problem to get hold of.
- MY models should have their rear torsion bars removed & refitted prior to the trip. These are a bitch to do at home, let along in the middle of the bush
- driveshafts/CV joints: if you suspect they may be an issue, replace prior to leaving, there shouldn't really be a situation where you can break them
repairs/replacement parts:
- replacement shock/struts springs (already assembled) depending on their current condition. you don't want to have to rig up solid stuff
- exhaust putty. good for temp repairs of fuel tanks too
- tool kit
A lot of stuff is common sense for out of the way places, but if you've never been there, it's not like any place you can think of.
Also, sharing spares between common vehicles is a good idea. not everyone is going to have the same issues.
Above all, vehicle prep must be meticulous. Spare parts north of Cairns are impossible to find without getting them shipped from Cairns (at ludicrous rates & time delays).
A tip for the women: on our trip they started rating the days by the number of sports bras they should wear;).
The corregations are hard on everybody.
The theory (and proven in practice) is that the suspension has harmonics in its operation. You want these to be in sync with the corregation's humps. Generally there are 2. A slower one (somewhere between 40 & 60) & a higher (between 80 & 120). It's trial & error to find these 2 particular speeds, & the car will shake itself apart at anything other, so you need to be able to "drive through" this shaking to find the harmonic. And every car is slightly different.
If you're lucky, you're trip might coincide with the road being graded, and most of this won't be an issue, but if not, be prepared.
sorry for the long post, just been there, done that, saw people literally crying at the end of some days.