General Duramax Information - Chevy and GMC Duramax Diesel Forum
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post #1 of 12 (permalink) Old 12-28-2013, 03:51 PM Thread Starter
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General Duramax Information

Hello everybody!

I believe that reading and understanding information allows people to make educated decisions. I prefer to give someone reading material, instead of giving them my opinion on a matter. What works for my truck may not work for a truck which is in a different climate, being operated differently, subjected to poor quality fuel, etc. For every link I post, there are many more out there, so keep searching and reading.

To start with, we'll cover the basics. The end of the thread will have a FAQ section.

If you have something to add, let me know!

***Matching Model Years with Engine RPO Codes***

RPO: LB7 (8th #/letter in VIN=1)
- 300 bhp (220 kW) @ 3100 rpm / 520 lb•ft (705 N•m) @1800 rpm
Fixed Geometry Turbocharger
Transmission: 5spd Allison 1000 automatic or 6spd ZF6 manual

RPO: LLY (8th #/letter in VIN=2)
- 305 bhp (227 kW) @3000 rpm / 605 lb•ft (820 N•m) @1600 rpm
Variable Geometry Turbocharger "VGT" (aka. VVT Variable Vane Turbocharger)
Transmission: 5spd Allison 1000 automatic or 6spd ZF6 manual

RPO: LLY/LBZ (8th #/letter in VIN=D) - LLY HP/TQ 310/605 / LBZ HP/TQ 360/650

Transmission: LLY equipped trucks are available with either a 6spd Allison 1000 automatic or a 6spd ZF6 manual LBZ equipped trucks are only available with a 6 spd Allison 1000
*This was a crossover period, much like 1988-1991 GM trucks (C/K/R/V). The LBZ was sold in 2007 "classic" body style Sierra and Silverado trucks.

RPO: LMM (8th #/letter in VIN=6)
- 365 bhp (272 kW) @3200 rpm / 660 lb•ft (895 N•m) @1600 rpm
Transmission: 6spd Allison 1000 automatic

RPO: LML (8th #/letter in VIN=8)
- 397 horsepower (296 kW) @ 3000 rpm / 765 lb•ft (1,037 N•m) @ 1600 rpm
*Vans and Cab/Chassis trucks, employ the LGH. (8th #/letter in VIN=L) 335 bhp (250 kW) at 3100 rpm and 685 lb•ft (929 N•m) at 1600 rpm*
Transmission: 6spd Allison 1000 automatic

-RPO Emission Control codes-
FE9 = Federal Emissions (example: EGR malfunctions are logged for later review, but do not trigger a CEL or decrease engine power)
NE1 = Northeast Emissions this covers NY, VT, MA, or ME
YF5 = California Emissions
VCL = a CFF (Clean Fuel Fleet) designation required to qualify for certain tax incentives (Commercial LB7)

-Emission control acronyms-
PCV- Positive Crankcase Ventilation (can be either vented to atmosphere or reintroduced to the combustion chamber to further reduce emissions)
EGR- Exhaust Gas Recirculation
DOC- Diesel Oxidation Catalyst
DPF- Diesel Particulate Filter
SCR- Selective Catalyst Reduction
VGT- Variable Geometry Turbocharger
CAC- Charge Air Cooler

Federal emissions controls: PCV (vented to atmosphere)/CAC
California emissions: PCV/EGR valve+cooler/CAT/CAC

Federal emissions controls: PCV/EGR valve+cooler/DOC/VGT/CAC

Federal emissions controls: PCV/EGR valve+cooler/DOC/VGT/CAC

Federal emissions controls: PCV/EGR valve+cooler/DOC/DPF/VGT/CAC


Federal emissions controls: PCV/EGR valve+cooler/DOC/DPF/SCR/VGT/CAC

Federal emissions controls: PCV/EGR valve+cooler/DOC/DPF/SCR/VGT (different turbocharger than LML)/CAC

!!! For those with a means of reading Diagnostic Trouble Codes (DTCs) via the OBD II port, H&S has compiled a very useful and well organized list of DTCs. !!!
DTC List


-Engine oil-
Oil filters.
Currently, GM's suggested/OE engine oil filter for the 6.6L Duramax is the AC Delco PF 2232. Because the engine block does not have an internal engine oil bypass, the PF 2232 has an internal bypass valve, set between 8-16 psi. This filter is compatible with all 6.6L Duramax engines (LB7+)

Bypass oil filtration.
Bypass filtration systems have been around for ages. Whether or not you need one depends on how often you change your oil, operating conditions, etc. The system's principles are simple: The oil supplied by the engine's oil pump is filtered using a "full-flow" filter. This filter filters all the engine oil passing through it. When engine oil is "cold" the pressures seen inside the filter are increased, due to increased viscosity. This increase in viscosity makes it harder to push oil through the filter and this can starve engine components of oil. In order to avoid staving the engine of oil, the "full-flow" filter houses a bypass valve. When open, the bypass valve will allow unfiltered oil to enter the engine. In the AC Delco PF2232 (OEM filter), the bypass valve is set between 8-16 psi. Until the oil is "warm", the valve will remain open. This is why a large percentage of engine wear occurs at startup. By taking a portion of the oil pump's output and filtering it through a secondary, low micron, high efficiency filter, the overall cleanliness of the oil in the pan is much better than with the stock system.

Reference: AMSOIL GM & Duramax 6.6L Oil Bypass Unit


Air filter elements. (Dry vs. Oiled)
A dry element will offer good filtration, excellent air flow and requires next to no maintenance. An oiled element will offer excellent filtration, good air flow and requires minor maintenance. An over oiled element will lead to fouled sensors downstream of the filter. Mass Air Flow (MAF) and Manifold Absolute Pressure (MAP) sensors may need to be cleaned more often when using an oiled element vs. dry.


Fuel filter change procedure. (LML used for pictures)

Best fuel filter.
As of May 4th, 2009, AC Delco's "new" TP3012 is GM's suggested/ORIGINAL EQUIPMENT. GM's original suggested/OE fuel filter for the Duramax engine is the AC Delco TP 1298. The TP3012 offers improved filter media and the addition of a coalescing layer. The coalescing layer efficiently removes emulsified water from the fuel, before it is introduced to the high pressure fuel pump. Water separation is instrumental in fuel system longevity. Caterpillar, Donaldson and other "large capacity" canister-style fuel filters may be used, with the addition of a fuel filter adapter. Info on the TP3012
NickTane CAT Fuel Filter Adapter:

Pre-filling fuel filters.
On a stock truck, fuel is drawn through the fuel filter, not pushed through it. Fuel from the tank enters the filter along the perimeter of the intake/discharge face. It is then drawn past the filter media and exits via the hole in the CENTER of the intake/discharge face. Any unfiltered fuel in the center of the filter will remain as such. Once the truck is started, this unfiltered fuel will be drawn through and pressurized in the high pressure injection pump, sent to the fuel rails and into the fuel injectors. Unfiltered fuel has been found to be detrimental to the longevity of the high pressure fuel system.

-Automatic transmission fluid-
Allison 1000 uses the Allison 29539579 spin-on filter. This filter cleans the fluid used in the valve bank (circuitry). There are cross-over numbers for other filter manufacturers, but the Allison filter can be found at heavy truck shops for a reasonable price. $8-$20 typically.

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-Fluid capacities-
-Engine oil w/ filter............................................ ..........................9.5 L/10 quarts
-LML Cooling system, Initial Fill.............................................. ........27.0 L/28.5 quarts
-LMM/LBZ Cooling System, Initial Fill.............................................. .24 L/25.4 quarts
-LLY Cooling System, Initial Fill.............................................. ........23 L/24.3 quarts
-LB7 Cooling System, Initial Fill.............................................. ........21 L/22.2 quarts
-Automatic Transmission, 1000 Initial Fill..........................................7 L/7.4 quarts
-Automatic Transmission, 5(DexIII)/6(DexVI) speed 1000 Total Fill .......12 L/12.7 quarts
-Manual Transmission, ZF6............................................... ..............6.2 L/6.5 quarts
-Transfer case.............................................. ..............................1.89 L/2 quarts
-AAM 9.25.............................................. ....................................1.7 L/3.6 pints
-AAM 11.5.............................................. ....................................3 L/6.3 pints
-Diesel Exhaust Fluid (LML Pickup and LGH Van).................................20.1 L/5.3 U.S. Gal
-Fuel tank.............................................. ....................................LB7-LMM: 6' box- 98.4 L/26 U.S Gal 8' box 128.7 L/34 U.S. Gal LML: 6' and 8' box- 136.3 L/36 U.S. Gal LML Cab/Chassis- 240 L/ 63.4 U.S Gal (Front: 89 L/ 23.5 U.S. Gal Rear: 151 L/ 39.9 U.S. Gal) ...if you have the capacities for the pre-LML Cab/Chassis, please send me a PM...

-Engine oil-
Best engine oil.
Although there are hundreds of oil choices and TONS of technology put into each and every kind of oil, too many people over-think this topic. Many have run nothing but "dino" oil and their engines are still going strong. That said, the cold weather and/or high heat performance advantages of synthetic engine oils are considered "necessary" for some people. Consider your requirements and make a choice.

-Engine coolant-
Duramax engines and cooling systems leave the factory with GM's Dexcool engine coolant. Dexcool should never be mixed with anything but itself, as gelling and chemical breakdown will occur.

-Automatic transmission fluid-
OE fluid.
Over the years, GM has used/recommended two automatic transmission fluids for use in the Duramax-powered, pickup trucks. DEXRON III(3) and DEXRON VI(6).
DEX III: Most GM user manuals for Duramax/Allison trucks between 2001 and 2005 suggest the use of DEX III. At the end of 2006, all DEX III product licenses expired and GM announced that they would not be renewed. GM then ushered in DEX VI.
DEX VI: GM user manuals for Duramax/Allison trucks from 2006+ suggest the use of DEXRON VI. DEX VI is 100% compatible with DEX III. Meaning, the two fluids may be mixed with no ill effects. HOWEVER, DEX VI will harden the "old", Viton seals found in transmissions originally designed to be filled with DEX III. The use of DEX VI in a "DEX III transmission" will lead to the hardening of the transmission's output seal and eventually, leaks. This hardening will take place over years, rather than months.
Allison Service Tip #1099J suggests that transmissions with the serial number 6310670488 AND UP, may be filled with DEX VI.
Official S/N breapoints for transmissions with DEX VI compatible seals are as follows.
1000 Series (GM Pickups) 6320784373 and up
1000/2000 Product Families 6310670488 and up
3000 Product Family 6510717281 and up
4000 Product Family 6610220990 and up
A very helpful ATF information thread: ATF fluid options: detailed information - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Transynd is a fully synthetic automatic transmission fluid produced by BP/Castrol. It meets Allison's TES 295 fluid specifications and is considered to be the best fluid for handling high temperatures in the Allison 1000. Although Transynd is not required by Allison, Allison allows an extended service interval if it is used. Do your reading though, as it may not the best choice for performance clutch materials in "built" transmissions.

Deep pans.

Transmission fluid capacities can be increased by using a "deep pan". Such pans are installed in place of the OEM pan. The factory internal/pan filter must be replaced with one designed to sit at the correct depth in the new, deep pan. Fluid is drawn through this filter, so it's correct placement in the new pan is a must for proper transmission function/longevity. Deep pans have reportedly kept the fluid cooler for longer, as opposed to drastically lowering the operating temperature of the fluid.

-Transfer case fluid-
OE fluid.
07- = Dex III or GM Manual Transmission/Transfer Case Fluid 88861800 (88861801 Canada) as per "GM Document ID #1897292".
07.5+ = Dex VI Automatic Transmission Fluid
From the factory, these t-cases come filled with automatic transmission fluid. Due to licensing changes around 2006 regarding Dexron III, GM released a service bulletin (Document ID #1897292) recommending the use of manual transmission fluid, in place of Dex III. This manual transmission fluid is: GM Manual Transmission/Transfer Case Fluid 88861800 (88861801 Canada). If the manual transmission fluid is not available, Dex III maybe used in its place. Dex VI may NOT be used if Dex III/88861801 is recommended, as Dex VI is not compatible with certain seal materials.

Some people choose to run synthetic 5W-30 engine oil in their transfer cases. I will let you read the info and you can make up your own mind, based on the operating conditions your truck is subjected to.
Reference: post #8 sheds some light on the issue

-Differential fluid-
These trucks ship with synthetic, API GL-5 75W-90 gear oil in the differentials. Synthetic fluids handle high heat along with cold temperatures better than conventional fluids, so consider your application when making a choice. Under extremely hot conditions, both ambient temperature and fluid temperature, a heavier fluid such as 75W-140 may be used. The heavier fluid may result in slightly reduced fuel economy during day to day driving, due to the drastically increased viscosity. Also, the heavier fluid won't penetrate small spaces as well as the lighter fluid, so make sure you NEED the heavier fluid before using it.
Something to consider when choosing "untested" differential fluids for use with an AAM 11.5" G80 is that some (if not most) GL-5 differential fluids do contain some limited slip (LS) additive(s). Mobil 1, Quaker State/Pennzoil and others do put right on the bottle that they include some LS additive. TYPICALLY, this small amount of additive is not enough to negatively impact the operation of your AAM 11.5" G80. Some experimenting may be necessary if you are wanting to use an "untested" fluid with your AAM 11.5" G80.

In an attempt to make choosing your AAM 11.5" G80 diff fluid hassle free, here is a small list of diff fluids that have been TESTED BY "DF" MEMBERS.
Note: Part numbers for 1 quart bottles
-GM RECOMMENDED: SAE 75W-90 Synthetic Axle Lubricant (GM Part#. 89021677. In Canada 89021678)
-Mobil 1 Synthetic Gear Lube LS 75W-90 (no part number yet, so please PM me if you have it)
-Quaker State SAE 75W-90 GL-5 Full Synthetic (Part#: 5066713) (I personally use this and have great results)
-Amsoil Severe Gear 75W-90 (Part#: SVGQT-EA)
-Amsoil 75W-90 Long Life Synthetic Gear Lube (Part#: FGRQT-EA)

Avoid additives.
While the front differential (AAM 9.25" IFS) is an open differential, the rear axle (AAM 11.5) typically houses a locking differential (Eaton G80). Trucks equipped with the G80 locking rear differential will have RPO code: G80 in the glove box. The locking mechanism, along with the clutch material in this differential have proved to malfunction when exposed to certain (most) LIMITED SLIP (LS) differential fluid additives. These additives have friction modifiers in them, which modify "clutch-holding" properties. Avoid these kinds of additives, along with fluids (synthetic and non-synthetic) that have large amounts of these additives in them. Violent locking and unlocking of the differential will result if certain "limited slip differential" additives are used. Some employees at auto parts stores confuse the AAM 11.5" G80 with G80 differentials from passenger cars and other vehicles, which DO require LS additive(s) to function properly. DO NOT LET A PARTS-PERSON CONVINCE YOU TO ADD LS ADDITIVE TO YOUR AAM 11.5" G80 DIFFERENTIAL. The G80's clutch packs are designed for use with either conventional or synthetic, API GL-5 gear oil. API GL-5 info: API GL-5: Clearing up the Confusion - Automotive Gear Oil Additives - Driveline Additives - The Lubrizol Corporation
Operation of an Eaton G80 Locking Differential: Inside the Eaton G80 Locker - YouTube

Large capacity differential covers.
The fluid capacity of the differentials can be increased by using an "large capacity" differential cover. These covers add a good bit of fluid. Like the transmission deep pans, large capacity differential covers keep the fluid cooler for longer, rather than drastically lower the operating temperature of the fluid.

Pump diesel.
Filling-up with clean fuel is one of the keys to increasing the longevity of your fuel system.

Lubricity of pump fuel.
The lubricity of diesel fuel is tested using a "micron scar" test. A hardened steel ball is pressed into and vibrated ACROSS a hardened steel plate, while submerged in a test fluid (diesel fuel in our case). The steel ball is later inspected and the size of the "wear scar" is measured, in microns. A low micron number translates into better lubricating properties, while a high micron number translates into worse lubricating properties. The American standard for diesel fuel is 520 micron scar, while the Canadian standard for diesel fuel is 460 micron scar. Some fuel suppliers will have "better fuel", but are only required to provide 520 scar fuel (USA). Producing fuel with lower scar ratings requires additives, and they cost money, so don't assume that all suppliers go above and beyond to bring you fuel well below 520/460 scar. Bosch states that their CP4.2 pump (found on the LML engine) requires a minimum of 460 scar rated fuel. Time to read.
Reference: Account Suspended

Certain fuel additives, under certain operating conditions, have been found to improve lubricity, increase fuel economy, reduce engine noise and reduce soot levels in the exhaust. Some vehicles benefit from using fuel additives, while others do not.

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-Front-end grease points-
2010 and prior:

The steering arrangement employed on these IFS (Independent Front Suspension) trucks may seem complicated at first glance, but in reality, the system is quite simple.
Steering shaft: Transmits the steering wheel's rotation to the steering box.
Steering box: Mounted to the driver's side frame rail, the steering box changes the axis of the steering shaft's input, approximately 90. Via hydraulic power and a mechanical advantage, the steering box also multiplies input torque. The high-pressure hydraulic fluid is supplied to the box by the power steering pump.
Pitman arm: Attached to the steering box's splined output shaft, the pitman arm is responsible for two things. First, converting the steering box's output from rotational into lateral (side-to-side) movement. Second, positioning, supporting and moving the centerlink.
Centerlink: Moved by the pitman arm, the centerlink shifts to the left and right, across the front of the truck.
Idler arm: Just as the pitman arm supports the centerlink on the driver's side, the idler arm supports the centerlink on the passenger's side. However, as the name implies, it does not steer the truck like the pitman arm does. Instead, it simply "idles" and follows the centerlink, providing support and maintaining it's lateral plane of operation.
Tie rods: Connecting the centerlink to both the left and right steering knuckles, tie-rods must be able to pivot up/down and left/right. This is achieved via tie-rod ends (TREs).
Reference: (great pictures and explanation)

Front (4x4).
The front axle is the GM AAM 9.25" IFS. These axles house an open differential, a reverse-cut 9.25" ring-gear and a reverse-cut pinion-gear.
In 2WD, the right wheel/axle is disconnected from the differential. However, the left wheel/axle remains connected to its side-gear in the differential. Because there is "nothing" connected to the right side-gear,the differential is able to rotate "freely". This leaves the carrier/ring-gear stationary, along with the front drive shaft. The engagement and disengagement of the right axle is carried out by an electric actuator, installed in the axle's housing. The actuator moves a shift fork side-to-side. This side-to-side action engages and disengages a set of interlocking gears.
*2010 and earlier differentials will not fit into the LML, 2011 and later case. The 2010 and earlier AAM 9.25, has a "split case" housing. To accommodate increased weight capacities and torque handling capability, the LML case (housing) is cast as one piece. A new differential was designed to fit the new housing. This "one-piece" housing does not have the space required to house the earlier differentials.*
Actuator assembly:

The rear axle is the GM AAM 11.5". MOST Duramax equipped pickups leave the factory with an Eaton G80, locking rear differential. Although very uncommon, some Duramax equipped pickups leave the factory with open rear differentials. G80 equipped trucks will have RPO code "G80" in the glove box.

Which shocks you replace your worn out factory one with is up to you. Some people are fine with new OEM units, while others choose aftermarket options for improved ride quality and overall performance. Rancho and Billstein offer what seem to be the most commonly used replacements.

Front torsion bar IFS (independent front suspension).
The front ride height of the vehicle can be adjusted a small amount by rotating the torsion bars, via torsion key adjusting bolts. Another way to raise the front of the vehicle is to install torsion bar keys. These keys replace the factory ones and rotate the torsion bars in the process. After an adjustment in ride height, the vehicle's front end must be aligned. Without an alignment, accelerated tire wear and undesirable handling characteristics may be experienced. A harsh ride may be experienced after using the torsion bar adjusting bolts to "level" the truck. This is due to the change in suspension geometry. Either a lift kit or new UCAs (upper control arms) will correct the suspension geometry, returning both handling and ride quality to OE spec.

Rear semi-elliptical leaf springs.
Trucks equipped with "heavy duty" leaf packages, like the DRW (dual rear wheel) trucks, have a set of helper springs bolted to the top of the leaf pack. All leaf sprung trucks can be lifted via "add-a-leafs", lift blocks or replacement leaf packs. Some owners choose to add aftermarket shackles, helper springs and/or air bags to increase payload capacity and load handling characteristics.

-Bolt patterns and lug nut torques-
Bolt patterns.
In 2011, payload and towing capacities were drastically increased. Along with a new, stronger, fully boxed chassis, a new bolt patter was introduced.
LB7(2001) to LMM(2010) SRW and DRW: 8x6.5" (165.1mm)
LML SRW(2011+): 8x180mm
LML DRW(2011+): 8x210mm

Lug nut torque specs.
1500(1/2 ton)-120 ft/lbs
2500(3/4 ton)-140 ft/lbs
3500(1 ton)-160 ft/lbs

-Head gasket grades/thinkess-
There are three factory head gasket "grades". The different grades, "A", "B" and "C", are used to identify the gaskets' compressed thicknesses. The reason for the three thickness options is piston-protrusion and the small, allowable tolerance between banks. At the factory, during assembly, piston-protrusion is measured on each bank and the "ideal" head gasket is selected. Many engines ship with two different grade head gaskets. This ensures that the best possible compression ratio is reached in each bank, without piston/valve interference. If the block and heads have not been machined, you may safely replace the head gaskets with "what came out". HOWEVER, it is common practice for DIYers and seasoned mechanics alike to use grade "C" head gaskets on BOTH banks. This way, even the worst cases of factory piston-protrusion become moot. A small reduction in compression will result, but not enough to be noticeable or cause harm to the engine.

For bored and/or milled engines:Block Over-Bored 0.010-0.030 in = 0.0394-0.0433
Block Over-Bored 0.010-0.030 in and Deck Milled 0.008 in = 0.0492-0.0532

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*Common issues*

-LB7(01-04.5) fuel injector failure-
Fuel injectors used over the course of LB7 production have been found to have internal issues. Internal components are known to "fail". The failures results in fuel leaks. A failed injector will allow an excessive amount of fuel to return to the tank. Also, the injector may leak fuel into the crank case, diluting the engine oil. The engine oil dilution often leads to overheating, head gasket failure, smoke at idle and accelerated engine wear. In response to the alarming number of injector failures reported, GM implemented the addition of a 7 year/200,000 mile injector warranty to the truck's original warranty. Injector balance rate tests are used by dealerships to diagnose failed injectors.
Reference: GM service bulletin -

-LB7(01)-LBZ(07) transfer case "pump rub"-
"Pump rub" is inherent to transfer case model numbers: 136, 146, 246, 261, 261HD, 263HD, 263XHD and 261XHD.
In our application, only 01-07 trucks equipped with Allison automatic transmissions are affected. The transfer case uses a gerotor pump to supply lube oil to both the drive sprocket sleeve and planetary gear set. Pump drive is attained by coupling the inner gear to the main shaft, via splines. The perimeter of the pump housing is composed of multiple tabs. These tabs rest in depressions, cast into the transfer case's tail housing, effectively clocking the pump housing while allowing it to "float". During operation, the tabs (and pump housing) move back and forth within their respective depressions. This movement slowly "rubs" away the parent metal of the tail housing. If left for long enough, this movement will wear a hole THROUGH the aluminum tail housing of the transfer case. The transfer cases leave the factory with an anti-vibration clip to keep the pump from moving. Unfortunately, the pump is still able to move with this clip in place. This small amount of movement is typically enough to wear/snap the clip off. Once the clip is broken, the pump is able to move even further, back and forth. 07+ transfer cases have a different tail housing and are exempt from this issue.

*"Pump Rub Fix": A few aftermarket companies supply "pump rub kits". These kits include a new pump housing, which replaces the factory housing. The aftermarket pump housing has much larger clocking tabs, which more evenly distribute force to the depressions in the tail housing. Replacing the factory/worn tail housing is also an option. New, updated tail housings are available. Installing a pump rub kit in a good condition, factory tail housing is also a viable option.

-LLY overheating (and head gasket failure)-
GM has released numerous bulletins with regard to overheating LLY engines. Although MOST LLYs do not suffer from overheating problems, nor head gasket failures, there have been many reported cases over the years. Poorly designed head gaskets, restrictive air intakes, insufficient cooling systems and in some cases, aggressive tuning and towing heavy loads, all contribute to the issues at hand. While some LLY owners have been able to remedy their overheating issues with a simple "mouth piece" upgrade, others found their remedy in adding a secondary (or heavily modified) cooling system. Warped heads are able to stretch head bolts. This can lead to "blown out" head gaskets. Conversely, a leaking head gasket can allow engine coolant to be both burned in the combustion chamber AND diluted by fuel. Once diluted by fuel, the coolant is unable to maintain acceptable engine temperatures.
Reference: (must read)

-Loose fuel injector electrical connection-
This is relatively common on the LLY platform. The contacts inside the electrical connectors can lose their "spring", causing connection issues. These connection issues cause the engine to act as if the affected injector is "dead". A DIY, temporary fix exists and is referred to as the, "Ice Pick."

*DIY Modifications*

-Legal headlight upgrade (OBS "Old Body Style")-

-High idle mod (LB7)-
Kennedy Diesel:

-Activating factory turbo brake (LBZ)-

-LLY Mouthpiece mod using LBZ mouthpiece-
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*Frequently Asked Questions*

Which modifications should I make?
First, decide what the truck's main use(s) will be. Carrying out modifications that will allow the truck/van to do a better job during everyday use will pay for themselves over time, and/or make the truck more efficient, enjoyable and useful. Second, find a source of available modifications. Research these modifications and decide which is best for you. A great source of available modifications are "build threads". A great example of a "build thread" is flyin6's LML thread.

Do I need a cold air intake (CAI)?
The stock intake assembly offers better filtration than any of the aftermarket assemblies. With the exception of the LLY, it is believed that the factory intake will support up to 500 hp. However, aftermarket CAIs offer improved air flow, support high-power engine builds and in some cases offer slight increases in fuel economy. The LLY's factory mouth-piece is relatively restrictive. Swapping the factory mouth piece for an LBZ/LMM unit has proven to decrease coolant temperatures and increase fuel economy. The extra air now available to the turbocharger also improves power output. There is also a small, inexpensive modification that can be made to the stock LB7 and LLY intake boxes. The modification allows more cool air from outside of the engine bay to be drawn into the turbocharger.
LLY reference:

Do I need a lift pump?

How often should I change my engine oil and filter?
Consider: emissions control systems, operating conditions, oil type, filtration type, etc.

Can I tow XXXXX lb trailer on "high power" tune?
First, understand how the tune increases power output. Second, understand which engine and transmission components are affected by such loads. Third, understand how these engine and transmission components handle increased power and heavy loads (HEAT!!!). Fourth, make an educated decision.

Are filters interchangeable across all 6.6L Duramax engines?
Yes. However, it is better to use "updated" filters on older model engines, opposed to "non-updated" filters on newer model engines. For example, using a TP3012("new") fuel filter on an LB7 is ideal, whereas using a TP1298("old") fuel filter on an LML is not advised. This goes for Allison spin-ons, engine oil and fuel filters.

Use the Driver Information Center (DIC) to determine maintenance?
This comes down to how the vehicle is being used and personal preference.

How much oil should my Duramax burn?
It is normal for the engine to burn approximately 1 quart of engine oil every 4-5 thousand miles. These figures will vary depending on operating conditions, fluids used and even engine to engine.

What is the best fluid for my Allison 1000 transmission?
5 speed transmissions leave the factory with Dexron III ATF, while the 6 speed variants are filled with Dexron VI. Choosing an aftermarket fluid for your automatic transmission depends on a few basic factors. Intended use, operating conditions, stock vs. aftermarket clutch material, etc. Transynd, an Allison TES 295 approved ATF, is considered to be the "best" ATF for a stock Allison 1000. Mike L sheds some light on this in the first link below.

How do I change the Allison spin-on filter?
The Allison spin-on filter is responsible for filtering the fluid used in the valve body (controls) of the automatic transmission. When the existing filter is removed, you will lose the fluid that is in the filter and the small amount that is sitting above it. Remove the "donut" magnet from the top of the filter (sometimes stuck to the filter head on the transmission), clean it and install it on the new filter (or back on the filter head). The fluid lost will need to be replaced.
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Last edited by JOKER; 02-06-2014 at 02:05 PM.
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post #6 of 12 (permalink) Old 01-14-2014, 04:13 PM Thread Starter
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Thanks for all the thumbs up, people. If you want something added/changed, post up and I will make it happen.
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post #7 of 12 (permalink) Old 01-15-2014, 09:17 AM Thread Starter
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Originally Posted by dukcaln View Post
great info, so is the HG for the lly a common issue as the injectors are for the lb7?

this is why we, the average reader and forum member get to learn and understand these trucks, thanks JOKER
While GM did publish a technical service bulletin about LLYs overheating, it only covered overheating in extremely high ambient temperatures. Because not many LLY power plants (compared to the number produced) have been plagued with overheating issues, I don't consider it a common issue. While the restrictive air intake (mouthpiece) is one contributing factor to the "LLY overheating phenomena", an LBZ mouthpiece swap will lower EGTs more than it will coolant temperature.

Purely for example:

Two of my personal friends each own 2005 LLYs. One of them has been stock since new and has well over 300,000 km on it. This one has been maintained quite well and tows a boat every now and then. At 300,000+ km, it shows no signs of overheating or HG leaks. The other one, was bought second hand around 100,000 km and came with a tuner. While buddy was on vacation with his family last summer, towing his holiday trailer, he blew a HG, bent two studs and warped the head. Power-adders certainly have something to do with it.
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post #8 of 12 (permalink) Old 01-18-2014, 07:49 PM
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Originally Posted by JOKER View Post
Thanks! It's tough to decide what is and is not considered, "general."
Facts about the duramax in its stock form is general info. Anything related to common issues is general info, but deserves its own section as you have broken this thread into. Repairs do not need to be discussed because every situation is a little different... This thread should be a useful tool for anyone just learning about their truck or buying a truck. You have done well as is so far joker.

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post #9 of 12 (permalink) Old 01-23-2014, 06:47 PM Thread Starter
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Originally Posted by beachman View Post
Great info! Answers a lot of questions in one place.
Thank you.

Any other "general" info a member like yourself would find useful if it were added?
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post #10 of 12 (permalink) Old 01-24-2014, 08:51 AM
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Originally Posted by JOKER View Post
Thanks for taking a peak. Your knowledge is always welcome!
Maybe add some additional torque info in the mechanical section:

2001 - 2007
Oil Drain Plug
62 ft/lbs

Manual Transmission NV4500 Hex Head (2001 - 2002)
Fill Plug 30 ft/lbs
Drain Plug 27 ft/lbs

Manual Transmission NV4500 SQH (2001 - 2002)
Fill Plug 30 ft/lbs
Drain Plug 30 ft/lbs

Manual Transmission NV4500 (2003 - 2007)
Fill Plug 27 ft/lbs
Drain Plug 27 ft/lbs

Manual Transmission ZF S6-650 (2001 - 2006)
Fill Plug 26 ft/lbs
Drain Plug 26 ft/lbs

All Transfer Cases
Fill Plug 15 ft/lbs
Drain Plug 15 ft/lbs

Oil Drain Plug
62 ft/lbs

Manual Transmission NV4500
Fill Plug 27 ft/lbs
Drain Plug 27 ft/lbs

Transfer Case NR3
Fill Plug 18 ft/lbs
Drain Plug 18 ft/lbs

Transfer Cases NVG261-NP2
Fill Plug 15 ft/lbs
Drain Plug 15 ft/lbs

All other Transfer Cases
Fill Plug 13 ft/lbs
Drain Plug 13 ft/lbs

2008 - 2010
Oil Drain Plug
62 ft/lbs

Transfer Case BW4485-NR3
Fill Plug 18 ft/lbs
Drain Plug 18 ft/lbs

All other Transfer Cases
Fill Plug 13 ft/lbs
Drain Plug 13 ft/lbs

2011 +
Oil Drain Plug
18 ft/lbs

Transfer Case BW4485-NR3
Fill Plug 18 ft/lbs
Drain Plug 18 ft/lbs

All other Transfer Cases
Fill Plug 13 ft/lbs
Drain Plug 13 ft/lbs

2013 Silverado 1500
275/60R20 AXTs, 2" level, UnderCover Flex, BedRug, WeatherTechs

2015 GMC Yukon XL SLT - SOLD
Husky Liners throughout, HID lows, LED fogs

2011 Duramax LML - SOLD
LTZ, Z71 pkg, VYU pkg, CCSB
AMSOIL in the diffs Edge Insight CTS FASS 150 FLO~PRO 5" exhaust H&S Performance LINE-X bedliner Mobil 1 5w-40 syn PPE Diff Cover Rough Country steering stabilizer TranSynd Trifold Tonneau Cover
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