Welcome to MiniMaxxtuner.com, where we’re doing a buyer’s guide on these classic body, style, 66, duramax trucks. This is just heavy chevy and gm trucks that ran from 01 to 07. and whether you want one of these, because the 66 duramax under the hood just sounds so good or that allison behind it is so legendary in the MiniMaxxtuner.com. You want to see what it’s all about. These trucks can be really great values, and even if you want to be like me and try to find one of those zf6 speed, trucks, they’re really nice to drive, and they have that independent front suspension.

That makes it drive a lot more docile than the other two brands. There’S a lot to be said about these, but they do have their quirks. So we’re going to look into those today and one thing we’re going to talk about – is the fact that these trucks, in their newest year at the time of filming, are 15 years old or they’re like this one they’re 21 years old right now. There’S things to look for if you’re buying one, but they can still be really good work trucks. So, let’s get right into it.

First thing i’ll mention is when you’re looking at a used vehicle, we want you to bring a scanner or an obt-2 sensor of some sort or, if you’re actually going to plan on buying one of these trucks. The edge cts3 scanner may seem like an extra thing. You don’t necessarily need, but it actually does a really great job of telling you what your truck is up to your coolant. Temperature is 49 degrees. It’Ll tell your voltage, your transmission fluid temperature.

It’S got a lot of information you can use and actually, in a little bit, we’re going to do an injector flow test using it. So if you’re planning on getting a duramax – and you want to run a gauge or a scanner pod like this edge gts3 – is a really good thing to both buy ahead of time and bring with you on your drive. So you can monitor all things, but at the same time it’s just also a nice thing to have. So when you own the truck, you can keep an eye on all the fluid temperatures and make sure your truck’s going to run as long as you want it to rust. There’S no real way to sugarcoat this.

I mean rest of this age of a truck is an issue and we usually say around the shop. Fender flares are not there because they look better than the paint fender flares there, because they look better than the rust. You can see on this truck, there was a line of fender flare, they took it off and surprisingly, the person actually did think it looked better than the paint, but usually those can be hiding something it’s surprising to see metal behind a fender flare, let’s head back, Because there’s a couple more areas right here is where all the salt gets kicked. So you want to check out the bottom of the rocker panels. These get quite rusty.
You’Ll see here, this truck’s got a bit of it. Starting bottom of the doors is an area you want to check for and under the door sills here you want to open it up and check underneath that rubber or around there to see if there’s any rust starting back here again, you can see there was a Fender flare here, as i said, it was actually covering paint. I guess he just really liked the look of fender flares, but you want to check in here. You want to check in here this lip can catch a bunch of salt. It can cause it to rust and that’s unfortunate to see if you’re trying to keep this truck nice tailgates on these trucks.

They have a bad habit of rusting down here at the corner. Starting there here or around the handle, this thing’s decently solid. But it’s something to watch out for if you want to make sure your tailgate’s in nice condition. You’Re also going to look for dents in any kind of panel damage that it’s been left open and backed into a tree or something, but the tailgate can be a high common area for rust. A good way to look at who worked on this truck is to double check in the bed to replace a lift bump or a gas pump.

If this is a gas powered body style truck, there’s a hole in the bed, that means the mechanic was lazy because there’s two ways to do it, you either drop the tank or you cut a hole in the bed and you find the pickup in the tank From the top it’s kind of just it could be that one mechanic doing the one job, but it kind of just shows the workmanship on the truck. So you usually see about a one foot by one foot panel: that’s been bent torn moved, cut and or jb welded back in place over where you’d find your gas tank. So it just shows the kind of workmanship on the truck. And if you want your bed to be in good shape, you might not notice it at first just double check that that’s not how they replace the lift, pump or fuel pump. If you decided, the body was okay on the truck you’re.

Looking at another thing, gm did that was kind of weird and you want to check all four doors or two doors depending on the cab setup. It’S the door handles. I don’t know how many different of these generation trucks, i’ve pulled. The door handle on and just came straight out in my hand, the plastic on these door handles is pretty cheap. I also recommend replacing it with a factory unit.

The aftermarket ones will break in like six or seven months these ones. If it took 21 years for it to break. Then it’s going to take probably another 21. If you buy it from the dealership. It’S a super simple fix, but sometimes they’ll, just plop them back on the passenger side door and hope you don’t go in that way.
Check every single door make sure the handles work same thing for the inside they’ll pull off all the time. So the handles on these trucks not sure what gm did for that, but they’re just kind of weak. This one might be slightly anecdotal, but i’m going to say it anyways, the duramaxes i’ve had experience with seem to burn out light bulbs faster than i expect. I don’t really see that it’s a problem, they don’t short, they just kind of burn out sooner than i think so. The duramax is that have quite a bit of light, so you want to double check when you walk around it, that they all work and then, as you own, the truck, you want to make sure that you’re, just on top of it [ Music ], so we’re In the cab, this is your proverbial home.

This is where you’re going to spend the most time. I’M just going to point out some common wear spots on these duramaxes power window switches you’ll see even this one’s a little bit loose. The very common problem on duramax is, i see it on almost every single one of these trucks in the old classic body. Stop really what you want to check for is, if it does come up, make sure that the little tab that it slides into isn’t broken from someone repeatedly smashing it into place without buying a new switch bevel. If it is, then you can’t really replace it with another one, because the place where it would go is gone if the little hole it’s a square hole.

That is where this clips into is still there. You can buy a replacement unit and be on your way, but that’s something. A lot of people will just smack on a whole bunch, and it kind of is unfortunate because it can make the truck feel not as good if it’s got a broken part on it. Here seat – bolstering, i don’t know how, but these trucks just love to disintegrate their seatbelt string, this one’s not bad, but you can usually see them quite torn the speakers on these trucks. I mean these door side.

Speakers seem to get kicked by every size. 15 work. Boot that comes in and out of these things, it’s just a matter of design, it’s where they had to put it it’s where it gets in a high traffic area, so you’ll see a lot of dirt, sometimes on these, and what people will do is they’ll balance. The speaker system away from the blown speaker, so what i would do is reset all the settings on the sound system and make sure this speaker here generally this one isn’t blown out it’ll kind of crackle. So this is actually one of our co-workers.

Trucks cory, you’ll, see them at the front desk and, of course, the speakers are working great, i just fired them up. The sound system is good. Next thing you want to look at is the stepper motors in your instrument cluster. You want to make sure that your tac, your speedometer your fuel gauge and all your temperature gauges work, because these trucks have a common issue of the stepper motor in the back of the instrument. Cluster will stop picking up the instrument itself.

Deboss garage has a really good video on youtube on how to fix that. It’S not the hardest thing in the world. It’S not the easiest thing in the world, but it’s something you want to look into just a very common failure area on these things is the gauges, so the stepper motor replacement kit, not that expensive something to work into the price. If you’re looking at one of these trucks, another thing you want to look at this switch gear here does a whole bunch of things. It’S your cruise control, it’s your wiper motors and it’s your signals.

It’S a lot of moving parts inside of the switch gear, so you want to make sure it’s also your high beam. So you want to make sure every single thing in here works. It’S just a matter of functionality, testing they’re decently, expensive to get from gm if they don’t work, but they are pretty robust. I’Ve just noticed a couple people that have had to replace them in their trucks like these and they’ve had to possibly buy two or three. It’S another thing that i really just recommend buying from the dealership.

They were the ones that built it. It lasted this long. It may be expensive to replace, but it’s likely to last the same amount of time or the aftermarket ones. I do sometimes find a higher failure point it’s just something to consider but make sure this stock, which does your intermittent wipers. Your high beams, your low beams, your signals and your cruise control busy switch, make sure it’s all functioning.

Now, i’m sorry corey! You did a really good job cleaning the truck last night, but unfortunately the roads are just terribly wet, so your truck isn’t as clean as it should be, but anyways the lb7 trucks, the early generation trucks, do have a common head, gasket issue. So when you’re looking at yours, if that’s the model that it is or even if it’s not you want to double check, your oil doesn’t look like a chocolate milkshake. You want to make sure it looks like golden oil or dark oil just as long as it’s not like milky and frothy. That’S that’s when you have a bad head, gasket issue or same thing with your coolant.

You want to make sure it’s that deck’s cool, color or you want to make sure it’s a solid color, not a milky, frothy terrible mess of expensive bills, another common problem with these trucks, the injectors are underneath the valve covers, and these injectors have a bad habit Of going unlike the later models, especially the lbz, where the injectors can be removed without taking the valve cover off it’s an in-depth process to replace one of these, i know corey had to replace it when he first got it later generations, they pretty much figure them Out we’re going to do a flow test as well when we’re in the shop so that’ll give us another idea of what’s wrong with the truck. If there are any injector problems, transmission fluid should be pink. Transmission, fluid should smell sweet, it smells burnt like burnt toast, truck’s, not having a stroke. It’S probably just slipping its transmission and it’s going to need to rebuild, but it also shouldn’t be discolored. Transmission discoloring is also a bad sign because it’s usually worn clutches getting mixed in with a fluid, so you should have a nice pink sweet smelling transmission, fluid!
If you don’t, the allisons aren’t cheap, they’re good transmissions, and that makes them not cheap. So something to watch out for on these trucks, [, Music, ], all right you’ve walked around the truck you’ve taken a look at the body. You like what you see so now you want to go drive it. What are you looking for? Well, if you have the scanner like the cts3 or the truck already has one you want to check the transmission cooler temperatures and you want to check the engine coolant temperatures both of those should sit around 190 degrees when they’re up to temperature.

You don’t really want them to go higher than that that can be cause or concern for bad cooling systems, transmission, overheating due to excessive load. Another thing that’s kind of unfortunate about the duramax and the allison specifically, is, if you have a tuned cummins with a 48 re or something like that, it starts slipping now. That will slip until it fails and that’s not really a good thing, but i mean, if you have a tuned truck that has a little bit of slip, because you’re making more power than the torque converter can currently hold it’ll. Let you still drive it if, if an allison detects any slip, especially like one two shifts three four shifts, and especially the four or five shifts in these older five speeds, it’ll put it into limp mode, so something you want to watch out for. I don’t believe this truck.

Does it it’s pretty good for that, but you want to watch out for the transmission run it through the gears. As i said, it’s not really a bad thing. It’S causing itself not to slip and wear out its clutches, but if you have a tuned truck you pretty much have to go for a tune or an upgraded transmission, almost right off the bat. If you put any kind of power towards these things. So it’s something to be mindful of the duramax doesn’t really have common drivetrain vibrations.

To look out for when i was talking with the cummins 48re and the third gens, the two-piece drive shaft will sometimes cause vibrations. That’Ll take out the tail housing. That’S something to watch out for the duramax doesn’t really have that as a regular common failure. Point vibrations, as you drive along, are usually caused by wheels on that particular truck or out of balance drive shaft from hitting something on that particular truck. There isn’t like a common, oh it’s going to vibrate and here’s what you look for.

The duramaxes are usually pretty solid drivers, but they do have an achilles heel, the steering box. What you want to look out for is hard points in the steering, if you’re doing a tight turn, and you want to look out for slop the truck kind of wanders all over the place. It could be your auto tie, rod ends and your ball joints being bad, but it also could be your steering box. We have replaced a bunch of steering boxes on trucks in the shop. We usually find that the duramax like from gm steering boxes, are the ones who get the longest life out of they have the least leaks.
We find a lot of leaks in aftermarket ones, but if you’re looking for other front end components, control, arms, ball, joints, wheel, bearings and outer tire rod ends, we really enjoy kryptonite products, they have lifetime warranties, they’re, really strong. We sell a ton of them, we put them on all kinds of vehicles that come through the shop, they’re really good for the rest of the components and they have lifetime warranties for the people who buy them, but we find for the steering box itself. We have our best luck with a gm steering box. They just seem to work best all right so now that we’ve driven the truck, it’s not showing us any bad signs, we are going to throw it on a hoist. There are common failure, points on duramax and this isn’t really just to buy them if you own a duramax of this bent generation.

These are things you should watch out for because they are common failure, points that could leave you stranded or with a big bill. So these are what we’re going to look for on the hoist we’re going to head over there in now, all right, just before we throw the truck in the hoist, we’re going to show you why we recommended bringing the cts3. Not only can you check all of your parameters, but you can also do an injector balance test so you’re going to swipe up on the cts3 you’re, going to go to diagnostics and you’re, going to go injector balance rates and click on it there you’re gon na. Let it pull up and you wan na see, plus or minus four anything outside of those rates means that injector is likely bad. That might be why it’s misfiring or smoking, or if it’s not, it should be a sign that that one might be coming up eventually.

You’Ll see all eight of the injectors on this truck are within that range. You usually want to do this at operating temperature in park, but this truck, as i said, it’s cold, because we know what the injectors had done before: we’ve measured it before [, Music, ]. All right, so i’m going to keep this one a lot more short form because there’s not too much. I want to show you underneath this truck, i’m just going to take a mechanic light and point out things that i’m aware of on these trucks. First off is the lower rad hose you’ll, see it there, it actually rubs up against the sway bar, and this one already has a bit of a rub into it.

So we don’t want to might want to replace it. What happens is it’ll rub through blow all your coolant out in one go and it’ll either seize your motor. If you don’t notice your temperature gauge get really high or it’ll just leave you stranded, because you have no coolant. It’S a very common issue on duramax’s of 01 to 07

I’Ve seen it happen on lbzs down to lb7s. They just happen to like rubbing those lines out.

Another thing that likes to get shorted or rubbed is this tcm harness that runs all the way from your transmission, your framer up to the front of your truck. It is a very common place for it to get rubbed anywhere there and the wires will short and cause your tcm to not shift right, have a limp mode cause. Something like that. Now the front suspension on these trucks are independent like more like a car setup than the live axles. The truck has so you want to make sure your upper lower ball joints.
Don’T have much play, there’s no ripped boots destroyed boots. You want to make sure that that’s all there because they do have a tendency to wander up here, you’ll see your tcm cooler lines. They run from your transmission they’re very susceptible to leaking here. These ones seem to be okay, but they do run along the transmission. The oil pan over your axle up past the steering and into your front tcm cooler or your transmission cooler.

Sorry, they are known to leak. So it is something you want to watch out for back here. You have your transfer case. There’S something called the pump rub. The actual hydraulic pump inside the transfer case will rub through the case.

You’Ll see a crack around there or you’ll see a big leak. You want to double check that that hasn’t happened. You’Ll notice here there’s a bit of a fix on the bottom. There might have been something that happened. They just wanted to fix that um, but you do want to make sure you check for that check the fluid to make sure it’s not metallic, or that there is some these outputs.

You have seals like anything. You want to check your output, shaft seal, your input to the front diff and your diff seal back here to make sure they’re not leaking check the shocks and springs, that’s regular car shopping. Really i want to point out the duramax specific problems, like those i said before, all right, so that was our take on the first gen duramaxes, the classic body style trucks. I’Ve owned a couple myself and then this is corey. So thank you for letting us use the truck for this video uh.

If we missed something, please let us know we, we don’t know everything, but we do have a bit of experience with these things and if you want to see another truck video buyers guide of show it down in the comments there thanks for watching. This is MiniMaxxtuner.com