Preventative maintenance - what is worth it?

Wheel bearings.

.
Battery?

Hi Joel,
Overhaul Brakes, replace, pads, fluid, (and make sure all slide pins are free, polish them up and HT grease them...) Also worth keeping bearings - if you can find out the exact ones you need - (about $10) and contacts for starter motor repair and bearings for alternator (cheap to buy) Air con tensioner pulley bearing etc etc Unfortunately its easier to source exact bearings from a bearing shop once the item has failed and you have it apart but you should be able to get specs for them easily enough.

How much you would be wise to do depends on some extent upon the routes you are likely to take. You can't carry everything 'just in case' , but if you plan getting off the beaten track, away from repair & recovery services then you need to be more self sufficient. Regardless of where you are going it makes sense to get all the basics checked & anything a bit iffy repaired or replaced before you go. Tell the folk who are doing the servicing of your travel plans & ask them to service the car accordingly. Always worth carrying spare belts & hoses. Ask the service folk to replace all belts with new & keep the old ones as emergency spares.
If the car has been fine without a catch can I wouldn't change now. Often a mistake to make changes just before you head off. Do it early just in case any issues arise so you can fix before leaving. Fitting a catch can on my car resulted in a leaking rocker box gasket.
Selling the car later is not relevant to what you do pre-trip. The idea is to leave with the car in the best possible condition for peace of mind. A secondary fuel filter is a good idea, but probably more so if headed away from civilisation to smaller, more remote communities. If you can, stay & observe the servicing so you at least have an idea about how to check wheel bearings etc. 6 months to cover what you are planning will likely be harder harder on the car than it has been used to, & thus more likely for anything that is a tad iffy to get worse/fail. It doesn't sound like you are a 'she'll be right' kind of person, which is good, because it's not the way to approach big trip prep. Get the top RAC cover, if things go pear shaped it's worth every cent. Also have a 'Plan B kitty'. On our first big trip we put aside the cost of needing a replacement motor in a remote area. We ended up needing it for precisely that reason.

Thanks, great advice!

hi
1/ given the price of fuel ,, inlet manifold clean ,pending on % blockage economy will return ,
performance /response will come back as well .
2/ no catch can if selling b4 another 100,000km
3/ valve clearances
4/ timing belt and tensioner
**both above if so equipped
5/ coolant flush /change with correct coolant type for vehicle
cooling system pressure test for leaks
6 / fan belts change
7/ spare belts and rad hoses
8/ new oils and filters incl power steer flush
plus cabin filter
9/ brake fluid flush including clutch hydraulics
10/ suspension / drive line /brake/ inspection and adjust and lubed

A fully serviced vehicle is everything inspected /serviced / repaired = no short cuts

If the vehicle has been regularly serviced by a good shop then you shouldn't need to look at anything. apart from what are terminated non serviceable items like starter motors, alternator etc, as they should be aware of common problem areas and be doing preventive maintenance.

Get the shop to do a thorough pre trip inspection of the vehicle, things can still go wrong but they should pick up any obvious issues.

If you have never changed the drive line fluids then it wouldn't hurt, but generally I wait till after a big trip to get them done as you may do water crossings etc.

If battery is tired then replace it, any sus tires replace them same for drive belts if reaching the end of their life.

I would avoid any major preventative work that's not required, ie clean of intake system, removal of injectors etc as your better off doing this when you can drive the car for awhile to ensure there are no issues with it after the work is done rather than just before you set off and find you have a problem down the track caused by the work that was done.

Take reasonable spares with you and tools, fluids, filters, drive belts, fuel tank and hose repair kits and tape etc. Spare brushes for alternator though you would be better off having it service before you could if its done 300000ks and parts aren't any good to you if you can't install them though may come in handy if you can get someone else to do the work if required.

With a vehicle that age and with very high kilometres, I'd be taking a couple of steering ball joints and a uni joint. Of course, you also need some equipment for replacing both.

I can recall a bunch of mates doing the CSR in 1980 with mostly HJ series Landcruisers. They all loaded up with tonnes of stuff (usually vast amounts of be-bogging equipment) - but no-one thought to take a spare steering ball joint.

Of course, one Cruiser busted a steering ball joint halfway up the CSR, and that nearly wrecked the whole trip, as they couldn't move with a busted ball joint, and another member of the party had to go into Newman to source a new one. The whole group had to stop until the ball joint was replaced.

A buggered uni joint won't stop you completely, but it can throw the tailshaft balance out so badly, you won't be able to drive over about 30kmh, and you risk other drivetrain damage by driving with a major tailshaft imbalance.
I've seen starter motors and alternators fall off with major tailshaft vibration.

Another thing to think about is the early DMaxes have weak rear diff carrier bolts. They were upgraded and strengthened from 2017. A busted diff is an unpleasant and costly experience, but at least with a 4WD, you can keep going.
Maybe carrying a set of new diff bolts could be advisable, because at least then, you wouldn't have to wait a week for them to roll up to your remote town location, at horrendous cost. This is something you have to cope with, especially in Northern W.A.

This bloke in the link below owns an earlier DMax, and has done for 5 years, and he outlines all the problems he and other DMax owners have encountered.

https://www.4wdingaustralia.com/4x4/where-does-the-isuzu-dmax-fall-short/

Cheers, Ron.