Re: THe NAC Lots-O-Post Thread
Good to know. I remember reading that somewhere that the early 12V are better than the early 24V (though i did read that sometime in the 2000s the 24V got better and they fixed all the problems or whatever. I don't remember details though.
Nope, but there's a couple issues with the 24V:
- VP44 Injection pump: Fragile. You get a 24V truck, you put a fuel pressure gauge on it immediately (though I haven't done this yet :doh

. If your lift pump begins to fail, the VP44 will fail soon after due to having to literally siphon the fuel out of the tank. The fuel keeps the VP44 lubricated. You won't notice a bad lift pump until it's too late, but you can tell early by looking at the fuel pressure.
- "53" block: Rumored to be fragile. Look for a "53" casting on the driver's side of the block near the oilpan, directly under the VP44. More information can be found
here.
- Runs cold: Not necessarily an "issue" but can be in the winter. My truck never got above about ~160 in the winter, so the heat wasn't that great in the cab. In the summer however, my truck only gets above 190 (operating temp) when I'm towing my XJ on the trailer (~6-7k), uphill, in 3rd gear, doing about 2000-2500 rpms. Again, not so much an issue unless you live in really cold climates where it doesn't get above 50* year round.
Edit: I just found a '98 with the 12V listing stating that 98 was the last year for the 12V. Did they swap to the 24V in 1998.5?
Yes 98.5 was the first year for the 24V. Check the above link on the "53" blocks...some late '97 12Vs have it though no reported issues.
Edit: And are the autos really all that bad?
YES. The 1st and 2nd gen autos are not that great. I believe the 3rd and 4th gen autos are better, but as soon as you add power to start towing a lot they aren't all that great. I know Travis's friend Scott had issues with his.
Basically, to play it safe, get an NV4500 (5-spd) or NV5600 (6-spd). Either one are practically indestructible. People are only starting to lose gears under ridiculous loads (which I'm more inclined to believe derives from a crappy rebuild).