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Pros and Cons of the LMM

BoostN

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What do you like about your Duramax LMM?

What do you dislike about it?

What is the most know issues?
 
I like that it is very quite. Going from the LB7 to the LMM was a definite change. The added stock horse power and 6th gear are nice. The fuel mileage is far from adequate. My LB7 lifted with 35's got better mileage than this stock truck. The darn ECM remembering your tune info is a pain too. Got to be really careful about mods now because the dealerships are telling GM on you and voiding your powertrain warranty.
 
Cons
- Rear seat folds up instead of laying flat like previous models.
- DPF...nuff said!
- Leaking Transmission cooling lines in cold weather.
- Fuel filter is much more difficult to get to.
Pros
- New look of body style
- Drivers area seems to be more comfortable then prior year models
- Overall creature comforts and dash layout
 
Pros:
quiet (especially compared to the 99 Dodge/Cummins that I traded in).
handles the trailer GREAT (not affected by wind)
G80 locking rear diff. :D
LOVE the backup camera - especially when hooking up the trailer or parallel-parking.
I'm back in a GM truck!
Bluetooth phone connection
remote start
LONG RANGE on the remote

Cons:
too quiet. Real trucks Rattle! LOL
did someone mention DPF? Well, I'll say it again. Darn fuel suckin, power robbin DPF!!
Can't sleep on that back seat!
Needs a bigger fuel tank (thanks DPF!). What's with all that wasted space under the truck where a bigger tank could have fit?
Speaking of wasted space .. there is that HUGE console with almost no storage space!
 
Anything more you guys can add to all this? I am going to be truck shopping here by the end of the week and I am stuck between an LBZ or the new body style and LMM. I do have EFI live and will put that DPF in the garbage... Any more info or considerations I should look at from the guys who have LBZ's and LMMs would be awesome. Thanks guys.
 
LMM has a better air intake system than the older models.

25" power sucking fan vs 21" on older models. Due to DPF and EGR cooler.

Temps won't stay reasonable when towing in 6th - have to manually drop it out of 6th or ECT temps skyrocket.

DPF NOT compatible with biodiesel as any used during regen exaust injection ends up in the crankcase oil.

Smokes too damn much under load towing hills then you are stuck in regen in town when the exaust temps are not high enough to work effectively. Due to too much EGR use in factory tune.

Regen cycles stink.

Heater hose can't take the high ECT's and split and are a pain to get to.

Passenger side battery is in a broiler and will fail first about 88K miles.

Heated washer fluid system burns the truck down.

Air bag module gets wet from carpet.

Oil pressure gauge is a glorified idiot light reading the same for 9 PSI as 30 PSI.

Downpipe from turbo to intercooler too small and burns wiring harnesses that can touch it.

Power steering hoses leak.

Fuel filter sucks, location sucks, WIF sensor a decorative in the way waste, and filter housings crack. Primer prone to failure as it works on unfiltered diesel - not even a tank sock. You will miss a lift pump...

Chronic oil leak at turbo inlet from PCV system that most dealers can't fix. Ditto for turbo to downpipe exhaust leak - did I mention it makes the DPF regen stink more?

DPF pressure sensor lines can break off road or running over dead deer in the road etc.

Fuel system has better injectors but good for only 200K before needing parts for pressure regulation etc - same as older years.

You can tune out the EGR without a blocker plate - done this and had it stay closed with crazy gonna break something power.
 
Will the LMM ECM log tunes? And will the Stealerships have a fit if I pull the DPF off and tune it out? I dont want them voiding warranties or anything like that... And is the LBZ an all around better package?

Let's put it this way...The LMM will remember what you had for breakfast two weeks ago. There really isn't a way around the ECM recording everything you do. If GM wants to nail you, they will. The LBZ is a little more flexible in terms of tuning but still can get you in trouble if GM digs down deep enough.
 
You have to pay to play. Want a warranty - leave it stock. Otherwise tune it and enjoy it as the 100K GM warranty isn't all that great in the first place. Till you blow an engine that takes the turbo with it or bust a transmission over a defect. Many wait till 100K to tune it.

Swap computers out with a spare set to hide a tune. That is until they pull the engine down and find an "overpower" type of failure anyway.

Most tuners go for overpower and give diesel boys a bad rep. So warranty claims are carefully looked over for this type of warranty voiding failures. Simply put the computer can be told to blow the engine and melt the transmission down by making way too much power. So the reputation is deserved.
 
LBZ was the best of the pre-DPF Duramaxes as far as reliability and power. LMM gets you an LBZ with the new body style as a plus (for those that prefer that style) and the DPF as a minus.
 
Anyone have any pros or cons to add? Im looking at a 2008 with 140k on it.

The MPG is way better on the newer DEF trucks. Mandated biodiesel use will end up in the engine oil: you will need to change it more often.

Are you going to delete it and block the EGR? After the EPA crackdown can you find a tuner that will let you delete it? Because I have emissions to pass I am a reason the non-emmisions trucks have a higher value and the 2008-around 2012 non-DEF trucks resale deservedly sucks.

At 140K I am replacing the HPCR injectors on my 5.9 Cummins. The DPF and cat are also expensive items on the 2008. Just saying.
 
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