What should I look for in a Duramax? Price?

I think I found a truck I like.

2007 Silverado crew cab 4x4. Very cleanly maintained. No rust, clean Carfax, perfect interior. It's got the LMM 365 hp 660 lb-ft engine, with the Allison. FX4 LT trim level. A few tasteful mods- pretty sure it is running a performance chip (appropriately tuned), large exhaust (which I could do without), and has a large Ranch Hand grill guard. Under hood and undercarriage show moderate level of dirt- appropriate for it's age, not off-roaded. Fluids not brand new fresh, but no burning smell, etc. No rattles, vibrations, leaks, etc. Shifts smooth. 180K. It's on a used dealer's lot, and they are asking $22,400.

So, what are a few things I should look for? I'm gonna have my diesel shop check it out (and tell me a little more about that performance chip , if it exists). Other than that, any specifics on this era Duramax?

The chip plus the exhaust is usually a warning sign for me, but I can't find any other signs of abuse. I like the power delivery, and would probably switch the exhaust (a little too loud for my tastes).

What would you guess it's worth?

Well the LMM is one of the better Duramaxes. That's what's in my GMC. The biggest issue with them are injectors, but it's not a common issue.

If it's got a tune and exhaust, that's not bad, that's a common power adder to modern diesel trucks today.

If it is '07 4x4 with 180k and they are asking $22k, that's right in the ballpark for price. It's actually a great price with all the mods you listed.

In reply to SyntheticBlinkerFluid:

Yeah, I drove an LBZ yesterday. Those 2 engines are supposed to be only 5 hp difference, but there was no comparison. The LBZ was OK, but had nothing to get excited about. This LMM has a huge kick in the pants- which is why I think it's chipped.

Just for comparison I bought my truck with 225k for $19k. It's and '08 Crew Cab long bed 4x4 Z71.

I bought an LLY (2005) crew cab, short bed, 4x4 SLE several years ago for $18k with 160k miles. At 210k now with nothing too bad to report. Replaced left side wheel bearings after hitting a pothole. Front brake calipers, but the problem ended up being a collapsed rubber hose. Tires....lots of tires. This thing burns through tires.

Looking around, it doesn't seem as if it has depreciated too much.

In reply to Tyler H:

Why would it burn through tires?

I put 80k on a set of Firestone Transforce HTs between March and December.

I guess you could say I burned through them.

In reply to SyntheticBlinkerFluid:

I'm pretty sure that is YOUR fault!

Assuming decent alignment, no abuse, proper tires for the weight range and use of the vehicle, no mechanical issues, etc., why would any particular vehicle burn through tires more quickly than any other?

Maybe Tyler H has been autocrossing his truck!

Or non-LT All Terrains. I have seen guys burn those up pretty quick. I just put a set of LT All-Terrains. They have a 50k tread life, so I'll see how that ends up.

SyntheticBlinkerFluid wrote: Just for comparison I bought my truck with 225k for $19k. It's an '08 Crew Cab long bed 4x4 Z71.

And surprisingly it fit in my garage. Though really height was more of an issue than its length.

In reply to petegossett:

Well to your defense, your garage is quite large. I'm actually jealous because I can't even fit my truck into my garage.

SVreX wrote: In reply to Tyler H: Why would it burn through tires?

Hot laps on CMP probably didn't help.

SVreX wrote: In reply to SyntheticBlinkerFluid: I'm pretty sure that is YOUR fault! <img src="/media/img/icons/smilies/crazy-18.png" why would any particular vehicle burn through tires more quickly than any other?

>7000lbs and >600 torque will do that. I run General Grabber ATS, why are soft for a 10 ply tire. Sometimes (okay, every day) I see two faint stripes pulling away from a stop, even with no squealing.

In reply to Tyler H:

I've found General Grabbers to not be a very good tire. Also the problem with any All-Terrain, is the softer compound than a Highway Tire, that's why the HT can get about 30k more miles than an AT style tire. Our trucks came with Bridgestone Dueler HT or AT depending on package IIRC.

I wanted to get another set of HT tires, but I've been hearing that this winter wasn't going to be good, so I opted for a set of ATs. I'll probably burn them off by spring, so I will be getting another set of HTs for the summer.

In reply to Tyler H:

I'd say that's a tire choice issue, not a truck issue.

My truck's curb weight is about 8700 lbs, and I do a lot of towing, but I don't have any trouble getting 40,000 miles out of the tires. But I run 10 ply highway tires.

07 is one of the prime years. All of the upgrades but before DPF. Dad has an 08 and its wonderful, but 14mpg.

In reply to curtis73:

Do you know if any of the after market chips and tunes can improve that fuel economy?

I care about fuel economy, although, at the moment I find myself caring a little more about emissions. My company pays for all my fuel, which is nice, but I am a little unhappy when I step on the accelerator and see a cloud of black smoke pour out of my 7.3. In the big picture, the emissions seem to be a way in which I impact the world around me negatively, which seems more important than a few dollars out of my wallet.

But, yes, I'd like better fuel economy (I'm used to the 22 mpg from my 7.3L). If there is a way to improve it, I will consider it.

Yeah, the part I hate about my 7.3 is emissions as well. I so wish we could love our old cars and not pollute as much.

In reply to SVreX:

Most of the "lower" subtle tunes are a towing/mpg tune. You're going to feel more power and much better mpg.

If you test drive the truck and it's pouring black smoke at any throttle, there's most likely a performance tune on it. If it only blows smoke at or close to full throttle, it's probably just a tow tune.

I had a "dirty" tune on my Duramax when I bought it. I could get 13 mpg towing and 24 mpg unloaded, but it would roll coal anytime I had to put my foot into it and if I hit a hill, the truck would drop into limp mode. I ended up finding out that the tune was supposed to have a controller (all the wiring was still in the truck) but the PO removed it, leaving it in a certain tune. I had my truck flashed back to stock. Now I only get 8-10mpg towing and 19 mpg unloaded.

Like Curtis said, 2007 is the sweet year, no DPF, but that doesn't sound like you'd have that problem with an aftermarket exhaust. It may have an EGR delete too if it has a tune.

I will be getting another tune on my truck. It seems to be commonplace anymore. I haven't decided on an EGR delete though.

In reply to markwemple:

I look at it like this: By driving and maintaining an old car that someone else might otherwise junk and replace with a new car were at least saving all of the energy/emissions it takes to build a new one. Same goes for using junkyard parts too I guess. No idea how the math actually works out on that, but it's something.

SVreX wrote: In reply to curtis73: Do you know if any of the after market chips and tunes can improve that fuel economy?

For the most part they all do. The two main things they focus on are fueling and injector timing. Since the factory tune uses very conservative timing to keep NOx down you can pick up significant power and MPG from bumping it up to where it should be.

Adding fuel (up to a certain amount) can actually add MPG as well, primarily due to higher peak cylinder pressures extracting more BTUs from the fuel.

Our 04 Dmax pretty consistently got 18-20 mpg stock. At about 100k we did 30-over injectors, air dog lift pump, intake, exhaust, and a 5-position chip. (stock, tow, economy, stage 1, stage 2). It now puts nearly 900 lb-ft to the wheels in position 5 and gets 18-20 mpg. Best I got in the economy setting (which pushes timing but not much fuel) is 21, but I only tested a few tankfuls.

In our case I think we could have seen much better MPG results if we had kept stock injectors.

Duramaxes with aftermarket exhausts have a relatively safe buffer of EGT, especially with the VNTs on the later models, but please be safe and install an EGT gauge. Turbos ain't cheap.

I care about fuel economy, although, at the moment I find myself caring a little more about emissions. My company pays for all my fuel, which is nice, but I am a little unhappy when I step on the accelerator and see a cloud of black smoke pour out of my 7.3. In the big picture, the emissions seem to be a way in which I impact the world around me negatively, which seems more important than a few dollars out of my wallet.

Something to put your mind at ease. The black smoke is actually not where most of your emissions are. That soot is heavy paraffins and polymers that basically fall to the ground quickly and don't do much harm. In fact, during black smoke production, the engine is operating at lower cylinder pressures and (although HC is spiking) NOx is greatly reduced. The truth is, all engines put out HC and NOx, so as far as EPA measurements the diesel doesn't look so good. But the EPA emissions tests don't take into account what happens to those HC emissions. A gas car running rich is putting out volatile vapors that hang in the air. Diesels put out heavy soot which falls to the ground and contributes far less to air quality problems than a gas vehicle.

In short, black smoke is not the awful thing everyone thinks it is. People smell the exhaust and see the black smoke and assume its awful stuff, but it really isn't as bad as a gas car with a spent catalyst or a vacuum leak.

Furious_E wrote: In reply to markwemple: I look at it like this: By driving and maintaining an old car that someone else might otherwise junk and replace with a new car were at least saving all of the energy/emissions it takes to build a new one. Same goes for using junkyard parts too I guess. No idea how the math actually works out on that, but it's something.

google hummer and prius emissions. Its not really equatable, but its pretty much on par; buying a new car vs. driving a 1965 Buick.

Just like buying an energy-efficient house. The greenest house is one that is already built and you upgrade it.

In reply to curtis73:

I agree, but I am going to take a bit of an exception.

In the case of houses, "green" is much too general a word. You are not going to get an efficient thermal envelope in an older house no matter how much you upgrade. But you will have an initial lower carbon footprint because of the materials consumption. That still doesn't mean you will have a healthier indoor air quality environment.

Yes, I understand about the black soot from a diesel. Doesn't mean a 7.3L is going to pass a modern emissions test.

In reply to curtis73:

So, how come you haven't upgraded your Dad's '08, if it's only getting 14 mpg?