6.6L Duramax LMM Maintenance Schedule & Service Guide

6.6L Duramax LMM Maintenance Schedule (Service Intervals)

"Severe duty" service conditions may include any of the following:

• Light towing that exceeds 1,000 miles during any applicable service interval.
• Medium to heavy towing or hauling payloads that place the vehicle near its maximum GVWR.
• Extended periods of idling, generally accepted as 10 minutes of idling or more during a 60 minute window.
• Driving off-road or in dusty conditions.
• Frequent driving in heavy stop-and-go traffic conditions.
• Driving in a manner that prevents the engine from reaching normal operating temperature (frequent stops and/or short trips).

Description	Service Interval(s)	Notes/Remarks
Replace engine oil & oil filter	10,000 miles/12 months or when "change engine oil" message is displayed by the oil life monitoring system	[1]
Replace fuel filter, drain water separator	15,000 miles	---
Replace engine air filter	45,000 miles	[2]
Perform engine cooling system service	150,000 miles	[3]
Replace automatic transmission fluid & filters	50,000 miles under normal conditions 25,000 miles under severe duty conditions	[4]
Replace transfer case fluid	50,000 miles	[5]
Replace front differential fluid	50,000 miles	[5], [6]
Replace rear differential fluid	50,000 miles	[5], [6]
Perform multi-point inspection	At oil change intervals	[7]

^[1] Do not exceed 10,000 miles between oil changes. More frequent oil changes may be advisable if towing frequently, hauling payloads near GVWR, or idling for extended periods of time. Recommend changing engine oil every 12 months if mileage does not meet service criteria.
^[2] Check air filter condition at oil change intervals and replace as necessary. Driving in dusty conditions will require more frequent air filter replacements.
^[3] At minimal, drain coolant from engine cooling system and replace thermostats, upper radiator hose, lower radiator hose, and replenish with new coolant/distilled water solution. Inspect remaining hoses and overflow tank, replace as necessary. Recommend that subsequent cooling system services are performed at 50,000 mile intervals after the initial 150,000 mile service.
^[4] Replace external and internal transmission filters, replenish with new automatic transmission fluid.
^[5] Replace transfer case and differential fluid immediately anytime these components are submerged in water; water infiltration is highly likely.
^[6] No service interval provided by GM; recommend replacing front and rear differential gear oil at 50,000 mile intervals to prolong life.
^[7] Multi-point inspection should include examination of ball joints, universal joints, CV joints, air filter, fuel system (leak detection), exhaust system, and vehicle brake condition. Grease applicable Zerk fittings as required.

6.6L Duramax LMM Service Parts List

Part Description	Part Number
Engine air filter	ACDelco A3087C
Engine oil filter	ACDelco PF2232
Oil pan drain plug	GM 11569943
Oil fill cap	GM 97350955
Fuel filter	ACDelco TP3018
Serpentine belt	ACDelco 6K1195, Gates K061195
Thermostat	Front	ACDelco 12T100D
	Rear	ACDelco 12T99D
Thermostat housing gasket	ACDelco 97223686
Coolant reservoir cap	ACDelco RC85
Upper radiator hose	2007 - 2008	ACDelco 24589L, Gates 23227
	2009 - 2010	ACDelco 24655L, Gates 23499
Lower radiator hose	ACDelco 26570X, Gates 23260
Glow plug	ACDelco 9G (replaces ACDelco 61G)
Automatic transmission filter, auxiliary (external)	ACDelco TF950, Allison 29539579
Automatic transmission filter, internal	ACDelco TF920
Transmission pan gasket	ACDelco 29549684
Front differential gasket	N/A
Rear differential gasket	14 bolt, GM 10.5	GM 26067159
	14 bolt, AAM 11.5	GM 12471447

6.6L Duramax LMM Oil & Fluid Specs, Capacities

Item	Oil/Fluid Specification		Capacity ^[1]
Engine oil ^[2]	Ambient temp > 0° F	SAE 15W-40 API CJ-4 or CK-4 Recommend Amsoil Max Duty 15W-40 synthetic diesel oil	10 quarts w/ filter change
	Ambient temp < 0° F (acceptable in all temps)	SAE 5W-40 API CJ-4 or CK-4 Recommend Amsoil Max Duty 5W-40 synthetic diesel oil
Engine coolant	50/50 solution DEX-COOL engine coolant concentrate and distilled water (GM DEX-COOL 12346290)		6.15 - 6.35 gallons
Automatic transmission fluid	GM DEXRON VI automatic transmission fluid (ACDelco 10-9243)		7.4 quarts service refill 12.7 quarts total capacity
Manual transmission fluid	N/A - manual transmission not available
Transfer case fluid	GM DEXRON VI automatic transmission fluid (ACDelco 10-9243) Recommend Amsoil Signature Series FE synthetic ATF		1.6 quarts
Front differential fluid	SAE 75W-90 synthetic gear oil Recommend Amsoil Severe Gear 75W-90 synthetic gear oil		1.8 quarts
Rear differential fluid	14 bolt GM 10.5	SAE 75W-90 synthetic gear oil Recommend Amsoil Severe Gear 75W-90 synthetic gear oil	3.2 - 3.5 quarts
	14 bolt AAM 11.5		4.4 - 5.0 quarts

^[1] Oil and fluid capacities are nominal; always fill to proper fluid indicator level (i.e. dipstick), fill plug height, or applicable level identifier. Vehicle should be parked on a level surface when checking or adjusting fluid level.
^[2] 15W-40 engine oil preferred in ambient temperatures above 0° F. 5W-40 is acceptable in all ambient temperatures, but only preferred (and required) when ambient temperatures are below 0° F.