Hi mate
I had a 1995 manual 3.1D bighorn for a number of years and only just got rid of it as she was getting overly expensive to keep going. Mine travelled literally the entire country top to bottom and spent a huge amount of its life in salt water which its fair to say she didn't much like. Everywhere we went was towing a small boat but a large amount of gear!
In over 200,000km I didn't have a single engine fault or problem that required any work - I couldn't say enough good thigns about the Isuzu diesels. However, a few things to consider: I went through a couple of clutches in the last 100k kms, the full monty inc hydraulics etc. Also, discs/drums were fairly regular casualties of the salt water despite fresh water washing.
I haven't gone for another bighorn though, depsite the engine being pretty much flawless, (I've gone for the Mazda BT50 ute over the D-Max). The main reason being that on the soft stuff the Bighorn is just a bit too big and heavy and I had a few tricky moments with beach launching. One particularly memorable one with Fisher involved waking a farmer up at 5am, dragging him down to the beach where the wagon was blowing bubbles through it's exhaust as it was underwater on an incoming tide!! But have got stuck a number of times on softer launches (Fletchers, Stony Bay etc) just because of the weight of the wagon compared to its 4wd ability.
Still, for the price they're good as gold and I was sad to see the old girl go (found out recently some boys up at Ahipara bought her and are using her on the beach every day!). Over a number of years she'd been from Bluff to Reinga via just about everywhere in between, most of the time with a fair load and apart from a starter motor dying once I never had a mechanical fault that caused a problem on a trip. So much so that I cancelled my AA membership (really!).
All that said, I can't vouch for the auto gearbox, but having done a couple of full clutches on the manual, I'd imagine you'd probably want to be prepared for some work there.
Hope that helps?
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