Duramax early 2000s

What is good, what is bad, what do I need to look out for?

Checking a HD2500 out today with a view to a new tow vehicle

There is a year where they massively improved the injectors, but I have no idea what year.

The LB7 motors from 00-03 are the ones with bad injectors that are in the head. More invasive than the later 04-05 LLY and 05-07 LBZ.

Not early 2k, but I have a cousin with one in the 2010-2015 range. It lost a fuel pump and dumped metal throughout the entire system. They had to replace pretty much everything. The repair cost was something like $9k. 

Update, 2001, 200k miles, black leather interior.

Problem, had a cracked trans pan, he swapped pan and then it went into limp mode. Suspect trans which seems logical

Price is very good

LB7 is 01- early 04.  These had the injectors that liked to fail.  If they've been replaced, it's good.  Fixed-geometry turbo, but you won't run out of breath unless you mod for more than about 600hp/1000 tq.  LB7 is praised for its lack of heavy emissions stuff and (aside from injector issues) the only real complaint is that it is the least quiet/refined.  Dad's LB7 has 200k, modded to 938 lb-ft at the wheels, and frequently tows 10k lbs.

LLY replaced LB7 in about April/May of 04 through end of 05.  Garrett VVTN is highly capable.  After learning their lesson with the LB7 injectors, they redesigned them and moved them outside the valve covers for easier repairs... but they likely won't need repairs.

LLY/LBZ  is 06-07.  Basically the same as the LLY from before, but they split them up into two different codes for different emissions classes and also into two different VIN codes; one for the 250hp vans and one for the 360hp trucks.  They did some other tweaks; little changes to the turbo, and went from a 16 bit ECM to a 32 bit for faster trim (tighter emissions and a little efficiency)  The LLY and LBZ from 05-07 are generally considered the "best" simply from the standpoint of being pre-DPF and netting you the more reliable injectors and VVTN Garrett, but all of them are brick E36 M3houses and will serve you well.

LMM started in late 07 as a heavily upgraded version to comply with the new EPA regs in 2008.  Added DPF which can affect MPG greatly for the first 30-50k miles.  After that it seems to not matter much.  It confuses all of us.

aussiesmg said:

Update, 2001, 200k miles, black leather interior.

Problem, had a cracked trans pan, he swapped pan and then it went into limp mode. Suspect trans which seems logical

 

Price is very good

Allison Transmission is pretty bulletproof.  Usually any faults with it are electrical.  Be aware that it is not cheap to rebuild.

Common failures:  Shift solenoid (B is the one that usually goes I think).  It will try to do the 1-2 shift, not see correct pressure, and goes into 3rd gear limp with "reduced engine power."  Another limp-inducing failure is the input shaft sensor.  When it can't verify that the input and output shafts are turning at the proper ratio, it assumes it's slipping and does the same limp mode.

If it's 4wd, be aware that there was a short run (usually 03-04) that had porosity problems with the T-case adapter causing them to sometimes crack.  It's apparently not a breakage issue more than an annoying fluid leak issue, but it's not just a remove/replace thing.  IIRC, for some reason the trans has to come out to do it.

In reply to Curtis73 (Forum Supporter) :

He stated it seemed to not be in 3rd gear limp mode prior to swapping the pan. Even with the pan gushing fluid.

In reply to aussiesmg :

I suppose it could have leaked enough fluid to slip which sent it into limp mode, but that usually gets reset after a key cycle.  Also, could be coincidence.  Also, could be that he fried it completely by letting it run without fluid.

Too many variables to know until you really dig into it.

I would honestly price it as if it needs $4000 worth of trans repair and hope to be pleasantly surprised.

My LB7 also saw failures in the FICM (injector driver module), fuel filter housing (would lose prime when shutting off) and it needed a steady diet of replacement glow plugs.  Supposedly all of these are relatively common.

Since I can't explain it any better than Curtis did, I'll just add that my LB7 was a wonderful truck, and I miss it. 
My only recommendation would be additional fuel filtration of some sort to save the injectors. Either an aftermarket lift pump (these trucks have no lift pump stock) or an auxiliary filter. At the very least, get an adapter to run a Caterpillar 2 micron filter. 

Dad went a little overboard on his LB7 with an Airdog pump.  He had the tank modified with a sump for a pickup, then an air dog lift pump which goes through two canisters; one filter and one water separator.  Way overkill, but supplying a diesel with clean dry fuel goes a long way toward injector health.

FWIW, the Duramax is my favorite.  It used to be the 7.3L powerstroke, but they are getting long in the tooth and they aren't quite as easy to make big power.  See also: noisy as berkeley.

Same goes for the 5.9L Cummins.  My favorite was the P-pump era for it's simplicity and ease of making gobs of power, but see also: noisy as berkeley and rattles transmissions to bits.

A D-Max van is on my bucket list.  I don't care if it is de tuned.

A 401 CJ said:

A D-Max van is on my bucket list.  I don't care if it is de tuned.

Me too, but it was either Dmax or AWD.  Since they never made that combo together, the AWD won.