[BlueMaxxxx]

Ok I do have the auto transfer case but Not the autotrak. The Manual still says use Auto-Trak 2 fluid which is the part # I listed above. Which was a pain to re-fill. I appreciate the tip on finding the drain plug on the rear end. That will make changeing the fluid a whole lot easier. My manual also says 80w-90 in the front axle and 75w-90 synthetic in the rear. Thats what I have used so far but I need to drain and re-fill the rear axle again and take a look at the cap on the front diff.

 

[chuntag95]

I have a 2500 HD ext cab SWB. I guess I gotta remove the skid plate and take another look at the front diff. When I drained it I just used the recommended conventional gear lube. The 4x4 unit which I though was a autotrac, maybee I'm confused though. It took a special blue fluid. GM part # 12378508 $6.96 qt. Do you have the shift on the fly ? Dave

There is a pushbutton transfercase that will shift on the fly, but is NOT the auto track. It uses standard Dexron III transmission fluid. The FRONT differential uses 80-90W Gear lube, but most go with the 75-90W or the 75-140 depending on location, towing, etc. As I recall, the manual is confusing about who has the autotrac, but it is not offered in the 3/4 and 1 ton units.

Oops. Left out an important word.

 

[BlueMaxxxx]

My manual says to put Autotrac fluid in the transfer case not ATF fluid. It does say use the ATF in the manual transfer case. Dave

 

[wlkjr]

Speaking of stinky rear end fluid, has anyone ever smelled any oil that smells good? It all stinks to me.

 

[Frank Blum]

BlueMaxxxx, there is only one type of transfer case in out truck. It is considered a manual by GM because you either shift a handle or push a button. Either will shift on the fly. It uses Dexron III fluid. Later! Frank

 

[dmaxalliTech]

OK, I am even confused now!!


Lets see if I can help confuse things further.


Front Diff-- OEM fluid is 80-90 gearlube. It is acceptable to replace it with 75-90 synthetic fluid. Any quality fluid is acceptable as long as it meets GL-5 requirements. When going to any type of synthetic fluid, its advisable to change the vent cap on the front diff to the "white" cap. This cap is the replacement cap and the black cap is no longer offered. Part No. 12479296 for the cap. The refill capacity for the front diff is 2 quarts.


Transfer Case- First, lets discuss the options for the transfer case. If you are driving a 2500 HD or 3500 pickup, you have a NV-263 case(push button shift) or a NV-261 case ( floor manual shift) There is no automatic transfer case in these trucks. The 1/2 trucks and I believe the 2500 (non-HD) trucks will use the NV-241 (floor manual shift), the NV-243 ( push button shift) or the NV-246 case ( auto-trak, push button ) We will concentrate on the 2500HD and 3500 trucks here. The OEM fluid for these is Dex III or equiv. This means that any quality Dex III fluid or synthetic will work. There is no changes necessary to switch to synthetic. Capacity is 2 quarts.


Rear diff- The 2500HD and 3500 trucks use an American Axle 11.5" rear end. Its available with the Eaton limited slip option (G80). The Diesel engine equiped trucks only come with a 3.73 gear. The 8.1 trucks have either a 3.73 or a 4.10 option. The OEM fluid is 75-90 synthetic lube, commonly referred to as "grape juice" for its smell. A synthtetic lube must be used in the rear axle and it must meet GL-5 requirements. I dont know the additive package of the aftermarket lubes but I would think that the quality lubes contain the necessary additives for the limited slip. It is not necessary to add any additive to the rear end when servicing. Capacity is 4 quarts. It is recommended by Eaton to service the rear axle after the first 500 miles of towing or 5000 miles of driving.


I hope this helps out a little

Eric

 

[BlueMaxxxx]

Arggghhhh !

My manual lists the two different fluids. Are they useing the same manual for the 1500 ???? So Do I need to drain out the GM part # I listed above which is the blue autotrac fluid and re-install ATF. If so I will definately use a synthetic. Man its a PITA getting the fluid back in that thing. Dave

 

[BlueMaxxxx]

Well I decided to go ahead and get the '04. The 04 Duramax manual has Vin id info and engine compartment schematics for both the LB7 and the RPO LLY. The bad news is that at 200 miles its pukeing tranny fluid all over the place

So back to the dealer tomorrow.