Christian,
All these engines are great in their own respect. If you are going to be in less developed countries where fuel quality and spare parts availability is questionable, I would favour 1HZ for pure simplicity and durability however the 1HD-T would be hard to go past. These engines are very very robust and forgiving. There is an old adage, the 1HZ will get you there in time...

On the other hand if you are somewhere where parts are not an issue, the pick of the bunch would have to be the 1HD-FTE but I would "settle" for the 1HD-FT. Many people don't understand what electronics drive the 1HD-FTE. The 1HD-FT is a multi valve with pure mechanicals and is a solid engine but was of limited availability (3 years in Australia) thus these engines are scarce and in very high demand this includes spare parts. Having owned both the 1HZ and 1HD-FTE my pick for pure driving pleasure (read torque, power and fuel efficiency) is hands down the 1HD-FTE.

One other interesting fact is that the base block for all four engines is essentially the same. The heads and internals were changed over the years. The other basic difference is that the 1HZ is an indirect injection design while the others are all direct injection engines.

Quote Originally Posted by alia176 View Post
Rumor has it that the 5sp manual tranny doesn't quite have the proper 5th gear for the diesel engine's happy rpm range. Evidently, that gear tends to over rev the engine a tad on the hwy.
The 1HD-FTE and 1HD-FT engines were both backed by the H151F a stout gearbox by any comparison. My 100 series is a 5 speed manual and the 5th gear is perfectly matched for this engine (cruising speed of 60 to 70 MPH).

Cheers,
P