Unless your mechanically inclined, the lb7 is a gamble. Even if injectors have been replaced. If they were cheap aftermarket units, it's no better off than it was before. I've had several customers learn this the hard way (they brought their own parts). Opening up the motor is fairly extensive so be prepared for a long haul, and do it right the first time.
Ask the person/place that's selling it to allow you to take it to a shop. Have the injector balance rates checked. At operating temp in neutral, any injectors beyond plus or minus 4mm3 - in gear, plus or minus 6, these injectors are bad. If they are more than halfway between zero and it's respective limit, it's fixing to be. A haze of gray smoke out the tail pipe will usually accompany this.
While the front end of these trucks can be tricky, they definitely have their advantages. Being independent suspension allows better grip in rough terrain. And if you've ever owned a solid axle truck and experienced death wobble, you'll welcome independent suspension with open arms. It just has to be maintained. Typically, if one piece is worn out, it all is. It's pricey, but fix it all. Don't replace one ball joint, replace 4. And never use house brand components on any 3/4 ton+ truck. Moog (or whatever is name brand elsewhere in the country) only. It's double the price for a reason.
The points about transfer case pump and encoder motors is spot on. Blower resistors, and the plugs melt. Instrument clusters fail frequently. All gm "drum in hat" ebrakes drag and wear out prematurely, even 1/2 ton. Definitely better off without emissions. And yes, it was lly's that overheat, not so much these. Seems like a long list, but ask me about my list for fords and dodges, just as long. Lol
Repowell, I would guess your extended crank and resulting pump failure were probably either an air leak in the fuel supply, or the suction side of the injection pump, which is my next suggestion to anyone. I would never own a duramax without installing a transfer pump. Gm is the only manufacturer that didn't use them. The injection pump has to siphon the fuel from the tank, through a (usually plugged up) fuel filter. A 24k psi pump with air bubbles in its lubricant isn't going to last long. With the resulting shards of metal, neither are the injectors.
Sorry dp, I have to disagree. I hate to hear you didn't have any luck with your lly. I just recently got rid of mine. 700 horsepower, daily driven for 2 years, not very lightly. No driveline or front end issues, or electrical, and the fit and finish was one of my favorites. And I've owned at least one of nearly all of the big 3's diesel trucks. The only issue I had was the one strong point that you encountered. The Allison won't hold much more than stock power without heavy modifications. At highway speeds I had to take nearly all boost out of tuning to keep the converter from blowing apart. Dodges are the same. This is one area that Ford really overkilled, thank goodness. My current truck is a 6.4 power stroke. The trans needs all its got.
Personally, I loved my duramax's. You can't beat the off-the-line power, which brings allot for daily driving satisfaction. Waiting on turbo lag gets really old. I would hesitate about the engine code, but only long enough to get the balance rates checked out. If they are near limits, use it to bargain and take the savings to a trusted shop. The rest of the mentioned issues can be a nag, but no worse than any other diesel, and even allot of gasser problems on a used truck
