Hi blokes (and ladies if any),
It's been some while since I signed in (years), but I have had it in the back of my head to post a ten year ownership report for posterity.
I bought the used 1999 red metallic U8 series V6 Jackaroo in mid 2003. I was actually looking for a '99 Nissan Pathfinder at the time, but test drove a 3.5L Jackaroo on a whim and that stopped all thoughts of a Pathfinder. I still remember the day well, I was on the way home from test driving a private sale Pathy, when I saw this Jack in a car yard with a very good price on it (compared to a Pathy of same age). What I remember was the very very casual sales guy (I HATE the pushy types), and the way the rear tires lit up when I left the yard car park when I gave it a bit, like I did with the Pathy earlier. The Pathy didn't wheel spin or course...
So the engine hooked me in, and the rest is history 
Now that I've had the Jackaroo (nick named The Battle Truck by some fox hunting pals) ten years I can say that it's good points are it's reliability and toughness and competence off road. Weaker points would be it's rubbery steering (which one just gets used too after adjusting the steering box as much as one can) and it's fuel usage. The diesel version would be much more economic, but can you drop the clutch one and leave two rubber lines up the road
Off road the V6 Jackaroo is quite a wonderful drive. I drove Patrols (GQ & GU) and older Landcruisers for work for thousands of dirt km's but always loved getting out on the dirt on weekends with my (much cheaper) Jackaroo. Both those 4WD's are tough, but the price for a similar age car put them out of reach for me. I also preferred the lighter mass and small size of the Jackaroo anyway.
The maintenance profile of the U8 Jackaroo is interesting compared to some of my friends 4WD's. I've not had to replace anything large on mine, a steering drag link pivot being the biggest item other than oil and fuel filters. (touching wood right now for luck).
I do ALL my own automotive work, most of which currently is on my daughters unreliable Daihatsu Terios 
I do oil and filter changes religiously at 10,000km, air filter cleaning (washable OEM type) after every second bush trip. I use fully synthetic oils everywhere but the diff's. I was using Mobil 1 in the engine but changed to Shell Ultra full synthetic when that got stupidly expensive. The minor oil usage typical of these engines actually dropped with the Shell oil. On that note, my 3.5L V6 uses about 250-350ml of oil over 10,000km. Which means it's on the dip stick's low oil mark as the next service rolls around. So a non issue really.
I've changed the diff oil twice since I bought the car (it had 70,000km on it then, and it has 200,000km now). I let the diff service slide a bit (OK a lot) until eventually I felt a very subtle rear end shimmy when turning sweeping corners at city speeds. When the friction additive used in these diff's wears out the LSD clutch plates bind and release in jerks causing this sensation (IMHO anyway). New oil and additive sorts that out no problem. I think I let mine go 60,000km BTW. The oil I'm using is Castrol LSX85W/140, and a cheaper Penrite version of the expensive GM additive.
The transfer case and gearbox has Castrol Syntrans 75W-85 in it, for the last 130,000km anyway. It's a nice oil and the gearbox still feels like it did when I got the car. You don't get cold shift baulking with this oil.
I've changed the oil twice in 130,000km.
The all the front drive shaft rubber boots were replaced at around 140,000km (IIRC) and are holding up fine still. A messy job but very cheap if you do it yourself. I also replaced the front hub rear seals and regreased the hubs (with Castrol HTB). The Jackaroo is still on it's original wheel bearings. I inspected them when doing the boots, and found nothing wrong so repacked them. The tricky part is doing the hub nut up with enough bearing tension to not allow free play in the bearings (and the big washer spin) but not make them wear out. I use about 2kg on a fish scale on a hub stud and found it about right (after finding 1.5kg too light).
I grease the tail shaft and transfer shaft U-joints about every 10,000km. I use the wrong grease apparently (a black moly type Castrol LMM) but did that for so long on so many previous cars with no issues that I just keep doing it, as I have not had replaced a U-joint since 1994 on a Datsun 200B SSS I had then.
The U8 is also on it's original clutch and original brake pads. I'm not sure how, maybe the OEM clutch disk is a big one anyway. I double de-clutch and blip the throttle on down shifts, that might have helped. I developed that habit from having a four speed Holden Torana with no syncromesh and some racing in my youth. The clutch has always had a bit of a shudder when cold though I must say.
I don't baby the brakes, but I do use the gearbox properly on long downhill descents, so maybe that helps too, or the OEM Isuzu pads are made from some exotic material. Dunno, I'll worry about that IF they ever ware out. Rotors are fine, I've never machined them.
Air conditioner has been fine, not been super powerful, but never needed maintenance either.
On my first long trip interstate not long after I bought the car I got a Check Engine Light on the dash and also had the engine stall a few times. The fault cleared by the time I got home a week or so later, but came back eventually. Turned out after a bit of analysis using an OBD-II code reader and a visual inspection, that the IAC vave and throttle body was coked up with EGR carbon. It gets into IAC valve body and around the valve seat on the TB as well and jams it fully open or fully closed. I removed the TB and IAC and cleaned it as fully as I could. While there I made sure EGR soot was no longer a problem in the future...
About 3 years later the same thing happened. This time it prooved to be just the IAC valve, again jamming on the valve seat of the TB. This time a clean in an ultrasonic bath with hot soapy water sorted it out. One thing more on that, if your IAC valve shows rubbing on one side of the valve pintle only it's sitting slightly off-centre in the TB seat. I altered mine by half a mm by pushing on the valve head sideways away from the worn side a bit and it's been fine ever since.
I have also replaced a rear window winder cable (that the kids broke) and that's about it.
Don't ask me about timing belt servicing (it will annoy some). I have a friend who's similarly engined Holden Frontera V6 is at 280,000km on it's original timing belt and tensioner bearings. I'm waiting to find out when his breaks...
The Jackaroo has taken some battle damage while I've had it (and from the previous owner) and taken it well. Last fox hunting trip an Emu sconned it in the front left guard, I was actually barely moving and it ran in the car full pelt. A battle scar as far as I'm concerned, pushed/pulled the most of it out with my hands and a big suction cup, left the rest. It has numerous deep scratches from Saltbush and some some close passes of barbed wire fences (I recommend avoiding the fences).
I once put the Jackaroo into a deep ditch at night while out in a big grassy paddock, I did it at about 40kph. Both passengers got some damage, I got a sore head. I though I'd be limping the 'Battle Truck' home that night for sure, but nope, reversed out of the ditch (left an great impression of the front bumper and grill in the dirt) and it drove away like nothing happened. Nothing happened to the front suspension at all.
The only suspension maintenance since new is a set of Munroe Nitro Charger gas dampers all round.
Over the years out bush I 'jumped' the Jackaroo four or five times accidentally when hitting wash outs in the paddocks at 80-100kph. The suspension has taken it all and not dropped a cm.
The V6 has been superb off road BTW, I rarely need to use Low Range to get up steep terrain, as the engine has so much low end torque (try that in a Patrol GU turbo...). I usually only use Low Range to stop cutting up tyres on really rocky climbs (or descents).
Tyres, I'm on the third set since I got it. Had Pirelli Scorpions on it when bought. Nice on road tyre, bad off road tyre (where I drive). I leaned how to plug tyres in a minute five from that set...
Since then I've gone Malaysian, with Sime Alpina and now a set of Silverstone AT-117's. It's rare to need to plug those during a bush trip, and even then usually only if driving through dry Saltbush in hot pursuit of a red fox. Dry Saltbush snaps with a sharp point and spikes the sidewalls/tread of nearly anything.
I'll try to post up a photo of the Battle Truck. You will see I am a minimalist 4WD'er. I try to avoid getting into so much trouble that I need a lot of additional hardware, or I only push the limits of 4WD when I have a buddy vehicle out with me. I don't get stuck often. One of my MUST have accessory items is a good UHF radio, and I have used it to call in a friend help on one occasion when I got the Jackaroo stuck in mud to the floor pan. The other thing I MUST have on a 4WD is a roof mounted Light Force spotlight. I have a 240mm size unit, and the in car control handle. Obviously it's used for fox hunting, but at night for dirt road driving it supreme at lighting up the road about 500m ahead from that height. I have no need for other driving lights when that's fitted. The fog lights I do have on it now are for lighting paddocks right in front of me, and allow me to drive paddocks with only parkers turned on other than them (slowly). This helps with night vision when on the hunt.
Oh dear I've been typing stuff for a few hours now. Gotto go do something constructive.
My last thought to put down is that I intend to keep the Jackaroo for many years still, eventually replace it with another Isuzu, maybe a used MU-X
Cheers and beers,
Martin
http://www.flickr.com/photos/mr_sneezy/12554402814/