First time Duramax LLY Owner with Questions

BigBlueGMC · 10-25-2009, 09:47 AM

Hi,
Let me start by saying I never owned a diesel truck before, so I don't know what to expect from it or what driving habit adjustments I need to make now that I own one!

I just bought a 2004.5 GMC Sierra SLT 4x4 crew cab with an 8ft bed!
It has the Duramax Allison combo.
It has 110K miles and seems to drive like new, except when towing!

I picked it up with my 2003 Chevy 2500HD (6.0 gas) 120 miles away!
I hooked the trailer to my new GMC diesel and loaded my 2500HD on the trailer.

I found that on level grades it pulled the trailer fine, but when on the highway and dealing with long inclines, I felt it did a terrible job of pulling on the inclines! Isn’t this where a diesel is supposed to shine!!!

Ok, with that said I checked the internet and found all kinds of articles slamming the LLY engine.

I also found a lot of articles and ads for an LLY Induction overhaul kit, True cold air intake, the Duramileage EZ tuner and many other upgrades. My pockets are only so deep so the big question is:

Are there design flaws with the LLY that should be addressed first and if so which ones are most important and which ones will give me better towing performance and a boost in HP and correct the things GM should have done in the first place???

Any and all comments would be appreciated!
I know there is a lot of info in this forum, but I can’t seem to find the answers I need, so I posted this thread to help me get my truck running the best it possibly can!

So which upgrades should I do first!!!

Thanks in advance,
Brian

**Dmax7511** · 10-25-2009, 10:07 AM

welcome to df

**la77chevy** · 10-25-2009, 11:05 AM

Theres lots of info on this, and several different options. You need to start with an upgraded turbo mouthpiece. Mod the stock MP, LBZ MP, Killler Bee MP, Kodiac MP and several others. Try searching these and decide which is right for you. I personally went with the LBZ MP. $100 bucks from stealership, lot cheaper than the rest.

While you're changing the MP, you should block the EGR (exhaust gas recirculator). You can pick up a blocker plate in the vendor section for under $20. Real simple install. You can search this also and find lots of helpful info.

**Hook'em_Horns!** · 10-25-2009, 11:21 AM

Attention: All LLY Owners

^^^^^ Change out the Turbo Mouth piece (and airbox mod) is all you need, altering the EGR will not yeild performance gains and will require additional $$$ to complete, not just installing a simple blocker plate.

BigBlueGMC · 10-25-2009, 11:32 AM

Thanks for the replies, keep them coming!

What's the point of blocking off the EGR.

As far as the mouth piece goes is the LBZ mp (will it fit without mods or cutting, etc) better than this setup -

Duramax Diesel Fuel Mileage Increase

It's the LLY Induction overhaul kit I mentioned earlier and was considering as my first mod, is the LBZ mp all I really need or is this overhaul kit better?
And what about this guys True Cold Air Intake, any good???

**Hook'em_Horns!** · 10-25-2009, 11:40 AM

The IOH kit is inclusive of the newer mouthpiece, altered intake tube, coupler, clamps, etc., to complete the 15 minute upgrade with clean looks without throwing any codes.

Others have acquired the newer MP and made alterations themselves to fit.

Making this needed LLY change will provide enormous changes in performance as well as turbo and engine life.

BigBlueGMC · 10-25-2009, 11:52 AM

So are you saying the IOH kit is better than just the lbz mp?
Any input on the TCAI they sell?

jc1843 · 10-25-2009, 04:20 PM

OK you did not state what your problem was towing-- I suggest that you repair the truck before you start adding other "Stuff". The LLY had some problems, like any vehicle, but most problems can be corrected. If you look for negative, you will find Ford has problems and Dodge as well. People usually do not post the good stuff and there are a million D-Max on the road.

Are there any codes?

Does the engine miss?

How much does the trailer weigh?

How long has the fuel filter been on-? ( these trucks demand clean fuel)

Is the air filter clean? (Is it an oiled filter?) oiled filters will affect the MAF reading!

Does it have large oversize tires?

All of these will affect the vehicle!

Get the vehicle running right FIRST!

BigBlueGMC · 10-25-2009, 07:22 PM

OK you did not state what your problem was towing
I DID YOU DIDN'T SEE IT
"I found that on level grades it pulled the trailer fine, but when on the highway and dealing with long inclines, I felt it did a terrible job of pulling on the inclines! Isn’t this where a diesel is supposed to shine!!!" LOSS OF POWER TOWING

Are there any codes? NO

Does the engine miss? DOES NOT APPEAR TO

How much does the trailer weigh? 9K

How long has the fuel filter been on-? ( these trucks demand clean fuel) JUST CHANGED 500 MILES AGO

Is the air filter clean? (Is it an oiled filter?) oiled filters will affect the MAF reading! STOCK FILTER BRAND NEW

Does it have large oversize tires? STOCK 265'S

YOU DID NOT CORRECTLY READ MY POST, I'M NOT KNOCKING THE TRUCK, IT JUST DIDN'T TOW AS WELL AS I EXPECTED IT TO. AND I WAS ASKING WHICH UPGRADES WOULD I BE BETTER OFF DOING FIRST, I DON'T THINK THERE IS ANYTHING WRONG WITH THE TRUCK EXCEPT FOR THE POOR AIR INTAKE DESIGN FROM WHAT I READ HERE AND ELSE WHERE ON THE INTERNET!
THANKS FOR YOUR REPLY!

bpe1 · 10-26-2009, 04:45 AM

my stock tires were 215x75. My truck does a fine job towing my 15,600 lb rv with somewhat over sized tires. Perhaps something is wrong with your truck. The LBZ mouthpiece was a great mod, runs cooler and lots more power. Best $100 you can spend on a lly.