Transfer case oil

[headymusk]

2001 duramax 2500HD 4x4 auto
Can someone tell me what other oil there is out there, besides Auto-Trak II, that I can use in my case? I can't seem to get any oil for it from my local parts stores. Nor do they have repair manuals such as Chilton for my truck. I feel like I have a concept truck or something. I can't even find how much oil the transfer case holds.

[DmaxMaverick]

DO NOT use Autotrac II fluid in your TC!! Your TC is not an Autotrac. Only 1500's and 2500's (non HD) have the Autotrac option. Dexron III is what you need. Same as what is in your tranny. Dino or synthetic.

[headymusk]

Why would my owners manual tell me to use Auto Trak II?

[DmaxMaverick]

It's the same owner's manual as for the 2500 (non HD). The 2001 M/Y manual didn't help much, which is why you should also have a supplement for the Diesel engine and Allison tranny. Even your original manual should recommend Dexron III for all but Autotrac, but it's kinda' vague reading. Autotrac was only an option for 1500 and 2500's. All 2001+ 2500HD and 3500 trucks require Dexron III (or Dexron VI on later models) for the TC, regardless of its operation (electric push button or manual shift).

[headymusk]

The required oil in my 2001 Deisel Supplement manual, under "automatic transfer case" says to use AUTO-TRAK II Fluid (GM Part No. 12378508). It says to use "DEXRON-III Automatic Tansmission Fluid" for the "Manual Transfer Case". Why would GM put out a manual and not really mean it or did they change their minds on what kind of oil to use?
I have a skid plate covering my front axle. Do I have to remove it to change the front axle grease?

[JohnC]

Does your 4WD selector have an "Auto" position? If it does not, it is a manual transfer case.

[headymusk]

AAAHHHHH! Now the light comes on! I wasn't aware that these trucks came with a "Auto" transfer. But, thanx for clearing that up for me. Do you have any idea where the drain plug is for the front axle?

[DmaxMaverick]

True. Your transfer case is a "manual" TC, whether you have buttons on the dash, or a shift lever on the floor. Manual, meaning it is a "dumb" gearbox. The Autotrac transfer case is operated with logic, making it "smart", able to engage/disengage according to traction conditions. That's where the owner's manual is vague. In any case, regardless of what you read or hear, unless you have an "Auto 4x4" button on your dash, you have a manual TC. If you have the "Auto 4x4" button, you don't have a 2500HD or 3500, and no Duramax Diesel engine or Allison tranny. The only practical difference between the NVG 261 (manual shift) and NVG 263 (electric shift) is the method the range is selected. Nothing "auto" about it.

[DmaxMaverick]

The drain plug for the front diff is at the bottom on the driver's side. If you have a skid plate under the diff, you need to remove it. No surprises with this service.

[headymusk]

Thanx to everyone! You are making my preperation for my 4500 mile trip to Wyoming to Arizona and back to Ohio a lot easier. Having a peace of mind while drinving in those kind of extremes makes the trip all the nicer!