Bad blocks can be in any turbo diesel from 1996 - 2001. If the 4th digit in the VIN is a Z, it means it was produced with a potentially flawed engine. If the 4th digit is an F, that is the newer block and you'll be fine. If the engine was replaced, obviously the VIN will not have been updated, so check the history of the vehicle. You may have to call AM General to find out. Lynch HUMMER can help you out with that as well.
The highest percentage of bad blocks seem to be in 1997 and 1998 models. Most of the engines that needed to be replaced had the engines replaced prior to reaching 30,000 miles. I do think I heard about one that had to be replaced in the 9X,000 range.
If you find a 1998 and it has a replaced engine, then you'll almost definitely be good to go.
Some people don't like the addition of ABS to the HUMMER line, and any HUMMER made 1999 or later will have ABS on board. The addition of lockers can help you out off-road, but those do cost money if not already installed.
Another key feature to look for is the 1997.5 upgraded HVAC. The HVAC system was updated halfway through the 1997 year, depending on where you live this could be important.
I love having windshield heat on my front windshields. I don't believe this was available until 1997, but in 1997 it was probably only an option, and not standard. I think even in 1998 it was also an option, I don't recall what year it became standard.
1996 is when a 2nd fuel tank was added, bringing the total capacity to 42 gallons (slightly less if you buy a 1996 gasser).
Check out Lynch HUMMER's website and read up on the H1 model year changes.
http://www.lynchhummer.com/changes/h...ges.index.html