New to Duramax

XB_Blaster

New member
Mar 26, 2021
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Getting on here to learn about the Duramax platform in the 2000s. I'd love a 7.3 Powerstroke but where I live people seem to think they are made of gold and not a machine. LMM back with exception of the LB7, not interested in that one.
 

2004LB7

Well-known member
Dec 15, 2010
3,143
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Norcal
Welcome. Looks like you want an LBZ then

Nothing really wrong with the LB7 other than the hard to access injectors. Put some SAC injectors in it and it is just as reliable as any other.

LLY, some overheating issues

LBZ, as good as it gets before the addition of the particulate filter

LMM basically and LBZ with a DPF

Tons more threads here to learn about each version. Any specific questions, ask on
 

XB_Blaster

New member
Mar 26, 2021
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Ok looks like the LBZ is only available for two years. That's like a 6.0 from 05-07, it kinda bottle necks me. Why does the LLY have overheating issues? Does the LMM constantly run the DPF to burn off the soot?
So looked on a couple sights and maybe the LB7 isn't as bad as I thought. Is it like the 6.0, had a few quirks early on but got fixed?

My goal is for light towing (track bikes, home materials) and durability and mpg. I live in Colorado Springs and commute to Denver so driving that far I don't want to replace the truck every few years. I will keep it stock mostly, I'm not against performance upgrades as long as they improve durability and mpg.
 

zakkb787

<that’s not me...
Sep 29, 2014
2,258
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Granite Falls NC
I would trade my lbz for an 02 lb7 in a heart beat. They are all good trucks with quirks. Lb7 has injector issues but with SAC injectors it can be remedied. LLYs had crappy head gaskets and a poor intake design that caused overheating. Both of those can also be fixed. LBZ is a great engine but does have worse pistons than the first few years. But the 6 speed is very nice. LMM is basically an lbz with dpf. No it doesn’t run all the time but it is one of the worse designs for emissions dumping fuel into the exhaust.
Lb7 is going to get the best mpg. But an LLY and up may tow better due to the vgt turbo spooling faster and the ability to tune in a turbo brake. Lbz and lmm have the 6 speed which some people have had better luck holding a little more power than the 5 speed plus it’s easier on the ears and engine when cruising.
 

2004LB7

Well-known member
Dec 15, 2010
3,143
157
63
Norcal
Others will know more but I believe the LLY had multiple issues, with each one contributing to over heating. Undersized cooling system, smaller (then LBZ) fan?, Restrictive air intake, increase in HP, maybe more. Seems like many end up doing multiple modes to try and correct it

Until the L5P, I think the LB7 is my favorite engine. Simplest of them all. I I said before, with the newer SAC injectors, it is just as, or more so, reliable as any other year engine. Less emission systems to deal with. The issue is the engine, and truck, is sitting at or near 20 years old now. If you are ok with that then don't overlook it as a viable truck

LBZ was kind of the last version before the emissions overhaul to add the DPF. LMM saw the addition of the DPF and redesign of the cab/body. LML improved on the DPF system and added some Nox reduction equipment. Redesigned cab and body again and beefed up frame

And currently the L5P with a major overhaul to the engine and emissions, cab, body, frame, ect. A very different truck the the previous years
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,812
255
83
Phoenix Az
Ok looks like the LBZ is only available for two years. That's like a 6.0 from 05-07, it kinda bottle necks me. Why does the LLY have overheating issues? Does the LMM constantly run the DPF to burn off the soot?
So looked on a couple sights and maybe the LB7 isn't as bad as I thought. Is it like the 6.0, had a few quirks early on but got fixed?

My goal is for light towing (track bikes, home materials) and durability and mpg. I live in Colorado Springs and commute to Denver so driving that far I don't want to replace the truck every few years. I will keep it stock mostly, I'm not against performance upgrades as long as they improve durability and mpg.
i wouldnt fret over a LLY. LLY heads seems to have a restriction in the cooling department that does not aid in them keeping cool. otherwise, their whole cooling system is the exact same as a LB7 and a LB7 even tuned to LLY power will stay cooler. in your case of what you want to do, i wouldnt even worry about it if you find a lower mile one for a good deal. just upgrade the intake horn on the turbo if it hasnt been already and drive it. 01-05 did have HG issues so clarifying if they have already been done is a plus.

LBZ is overrated due to people not actually doing their research. They are more prone to break a crank, weaker pistons, hg and injectors are jsut as likely to go out as compared to a LLY or LB7 (after 200k, return rates start to go out of spec) but they do offer more hp than older gens, last model before DPF, 6 speed trans, and some other little things like lack of FICM and so on.

LMM is the exact same as the LBZ with small differences. they do come with a DPF and use diesel fuel to run regen on the filter. its done by injecting fuel in on the exhaust stroke of the engine. Not ideal for engine longevity but ive not heard many people complaining of higher mileage LMM's having worn out engines due to washed cylinders
 

XB_Blaster

New member
Mar 26, 2021
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Got a little confused in your post, if i find a LLY or LB7 with low miles it wouldn't really matter? Or did you mean both? You mentioned HG twice, what is that referring to? So LBZ's are gonna need serious work after 200k is what it sounds like. LMM is not ideal but I'm a realist and if that's what's available in my area at the right price I wanna be prepared.
 

XB_Blaster

New member
Mar 26, 2021
5
0
1
I would trade my lbz for an 02 lb7 in a heart beat. They are all good trucks with quirks. Lb7 has injector issues but with SAC injectors it can be remedied. LLYs had crappy head gaskets and a poor intake design that caused overheating. Both of those can also be fixed. LBZ is a great engine but does have worse pistons than the first few years. But the 6 speed is very nice. LMM is basically an lbz with dpf. No it doesn’t run all the time but it is one of the worse designs for emissions dumping fuel into the exhaust.
Lb7 is going to get the best mpg. But an LLY and up may tow better due to the vgt turbo spooling faster and the ability to tune in a turbo brake. Lbz and lmm have the 6 speed which some people have had better luck holding a little more power than the 5 speed plus it’s easier on the ears and engine when cruising.
Can well I won't be towing that much weight, 5-6k at most, so sounds like the LB7 got a bad rep. Would studding the LLY help the head gasket issue?
 

XB_Blaster

New member
Mar 26, 2021
5
0
1
Others will know more but I believe the LLY had multiple issues, with each one contributing to over heating. Undersized cooling system, smaller (then LBZ) fan?, Restrictive air intake, increase in HP, maybe more. Seems like many end up doing multiple modes to try and correct it

Until the L5P, I think the LB7 is my favorite engine. Simplest of them all. I I said before, with the newer SAC injectors, it is just as, or more so, reliable as any other year engine. Less emission systems to deal with. The issue is the engine, and truck, is sitting at or near 20 years old now. If you are ok with that then don't overlook it as a viable truck

LBZ was kind of the last version before the emissions overhaul to add the DPF. LMM saw the addition of the DPF and redesign of the cab/body. LML improved on the DPF system and added some Nox reduction equipment. Redesigned cab and body again and beefed up frame

And currently the L5P with a major overhaul to the engine and emissions, cab, body, frame, ect. A very different truck the the previous years
L5P is way over my price range, I'm ok with twenty year old truck because I can get parts to update things that need replaced. As long as it isn't rusted out I should be ok.
 

2004LB7

Well-known member
Dec 15, 2010
3,143
157
63
Norcal
I would say, any duramax year that is in good shape and under the mileage you are looking for should be a candidate for purchase. All have their own quarks but can all be delt with. Don't be scared about any of the "common" issues discussed here. While they may be more common to that model, they are still less then 1% of the trucks.

If you find one in your price range that meets all your other requirements, get it. We can walk you through any of the repairs if needed and upgrades you want. When properly cared for and maintained, these engines regardless of the year will last a long time. Upgrades or not

Head bolts are nice but not needed for the LLY. Properly torqued new head bolts will work just fine. If you are fine doing your own work you can probably find a good deal on one that the owner had given up on or doesn't have the money to fix so is selling it cheap. This was common a few years ago for the LB7 with its previous injector issues. Many weren't willing to spend $4k or more to have a shop replace them. But doing it yourself it could be done for less then $2k. There are still a few out there but are becoming harder to find. So a newer year may be more available. Kind of depends on your location and how far you are willing to go to get it

Doing the work yourself will give you more experience and confidence in your truck then any book or internet post could ever do. It can be very rewarding

Have fun shopping. Don't be scared
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,812
255
83
Phoenix Az
Got a little confused in your post, if i find a LLY or LB7 with low miles it wouldn't really matter? Or did you mean both? You mentioned HG twice, what is that referring to? So LBZ's are gonna need serious work after 200k is what it sounds like. LMM is not ideal but I'm a realist and if that's what's available in my area at the right price I wanna be prepared.
a low mile LB7 or LLY will work just fine for you. LB7 will need SAC style injectors to correct all its "horrid" injector issues. LLY, just follow as i stated. HG is head gasket. i wouldnt call replacing injectors serious work, more that the engine isnt what the internet says it is. I wouldnt be scared of a LMM. i know of quite a few that have been awesome trucks, their weak points are just the same as the LBZ.
 

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