TowRig.com - Diesel Discussion and Tow Tech

Ok, this came up in private discussion, but what do you guys think about the differences between the Duramax versions.

My take:

LB7: This is the original, available in 01, 02, and part of 03. Not sure exactly where/when it was completely replaced. It has "internal" injectors requiring more effort to service or replace and a slightly lower power rating. The '01 had "first gen" injectors that were much more problematic and likely to fail. Late '01 and all later versions had the "second gen" injectors that reduced problems, but were still internal. Over all, the best engines for dependability seem to me to be the LB7 with second gen injectors.

LLY: This replaced the LB7 and had slightly higher output, but the main change was to make the injectors easier/cheaper to service. However, the new injectors seem no better than the "second gen" injectors, and over all stability seem to be no better. I've also seen opinions that the changes in the LLY seem to have made it more susceptible to drivability problems and such, but it's been a long time since I kept up, and I don't recall for sure exactly how that stacked up.

Also, the LLY has a slightly better transmission due to tweaking the line pressures upwards, but still not that much stronger and is considered about the same when evaluating the "safe level" of increased power. And early ('01 only?) transmissions had relatively frequent problems with the TCM (or one of it's components? don't remember, some electronic piece on the trans).

Oh, and the last thing I can think of on the DMax trucks, the early '01s had a problematic 2 piece drive shaft that got a TCB to replace with a 1 piece design.

Anyone with more info for those looking for used Dmax trucks?

I wish I could add something of value to this thread but I only have experiance in driving my 05 LLY.

I had issues with 'dirty' fuel alowing the injector to stick open casuing MASSIVE amounts of smoke to bellow out the back, smoking out a 4 lane hwy as far back as I could see:doah:
Was this just dirty fuel? or does the injectors have something to do with it? Too sensitve when the fuel doesn't lubricate properly? Don't know. As I have said before, Stanadyne is a wonderful thingwaytogo

Didn't the LB7's injectors leak and fill the crank case with diesel?
On my 05 they replaced the blue turbo hose with an alluminum one.

I like to think that 'evolution' plays into 'why' an 05LLY is the best of the Dmax configurations out there. Engineers are drivin by the 'number crunchers' and 'bean counters', they are also improving the products thru R&D, surveys, service history that captures common or widespred problems are going to be addressed in the 'next' production line. Of course not all squeeky wheels will get oil but they will prioritize all the issues and work their way thru the list of 'known issues' to help prevent warrenty costs and such.
So even though my 05LLY is brand new, it is still 5years old sence it was 'born'.
You dig?

Unfortunately, not all "evolutionary" changes are in a "good" direction, in part due to those bean counters. I know lots of people were upset with things like loosing the cabin filter, service lights, and such like. And the LLY has a fairly good laundry list for the detractors. <shrug> I'm not sure that it's not just a wash betwen the LB7 and LLY. I also recall that the LB7 is more responsive to "bombing" as well.

On the leak thing, both the LLY and the LB7 can flood the crank case with fuel if the injector sticks or for certain types of leaks. However, there cap nut seal (or whatever it is called) will no longer dump directly into the crank case like the LB7 would, but that generally does not fail in use, only when improperly installed during servicing. At least that is what I recall posed by some GM service techs on TDP way back when the LLY was first coming out. So I think this point is largely a wash as well.

In summary, as far as I know, there is no appreciable difference in LB7 and LLY in power, dependability, or cost of operation (though injector replacement is slightly less expensive). The only one to be thinking about is the '01 if it has not had the injectors replaced.

On contamination. Some of the Racor filters have been found to rust inside, even on the "clean side" apparently. And Racor makes them all (even WIX) IIRC. And there have been cases of very low mileage injector failure where some sort of residue was found in the injector lines, probably from pre-production handling or maybe some sort of oxidation. Again, this is just hear-say from reading posts on "the place" and TDP, but much was substantiated by the actual techs doing the work.

If you were looking at a '03 Dmax how do you know if its a LL or a LB engine?

You either have to know the visual cues, or check the VIN. Not sure how to describe what to look for on the engine and I don't remember the VIN code, but you can probably find in on the internet. VIN code is probably the best because then you could check over the phone/net without having to see pics or go there...

If you were looking at a '03 Dmax how do you know if its a LL or a LB engine?

All 03's were the LB7. Some early 04's were LB7, rest were LLY.

VIN is 8th digit. 1 is LB7 - 2 is LLY IIRC.

John

Oops. I thought I remembered the LLYs starting to appear in '03. So much for my memory. Thanks for the correction.

Some might argue that a 49 state LB7 would be better because it does not have EGR or a catalytic converter.

I am a little leery of the VVT on the LLY, more stuff to break, and I think that's one of the reason the LLY doesn't respond to chips as well.

Marc

Bought my truck on Dec 29, 2003 and it was 2004 Lb7. About a month later I found out that all trucks that went down the Assembly line after Dec12, 2003 were LLY's. At first I was mad but my mileage seems to be 2-3 mpg better than the LLY's

I may look for a late '03 LB7 in a low mileage 49 state truck. I would think that it should have all the updates by then. Then send some of the savings over a new truck for some goodies from Banks. I like the looks of the PDA instead of gauges. waytogo