Quote from the GM tech link: "On 2005 Chevrolet Silverado and GMC Sierra 2500/3500 Series Pickups equipped with the 11.5-inch ring gear rear axle assembly, the factory lubricant fill level may appear lower than the published specification. This axle can be identified by the location of the fill plug on the rear axle housing cover, instead of on the front of the axle housing."



My question:
I have an 04 K2500HD with D-Max/Allison/limited slip, and the fill plug is on the front of the axle housing, so what size rear diff do I have, and the second question is should it be filled to overflowing, or follow the directions for the 11.5" ring gear rear axle, which says to put in 3 ltr of synthetic SAE 75W-90 gear oil?

Does it not have a plug on the rear cover? The only rear available is the 11.5"

I am a dunce. http://www.dieselplace.com/forum/images/smilies/duh.gif I just looked at my rear diff and the plug is on the cover. I would have sworn it was on the front of the diff when I filled it. I should have filled my wine glass after I filled my diff instead of before. So I guess I have the 11.5" one. Thanks

I may be wrong, (But I don't think so!) There is just one differential that comes with the Duramax/Allison, or 8.1L Gas/Allison, or Duramax/6 speed, or 8.1L gas/6 speed combo. It is the 11.5" 3.73:1 American Axle. This axle is in both the 2500HD and the 3500 trucks equiped with the combo`s I listed above.

The 2500HD with the 6.0L gas/ 4 speed auto has the smaller ring gear differential. (I think it is either a 10.5" or 9.5") I am not sure about the 3500 with the 6.0L gas engine, or if it is even standard on that truck.


Quote from the GM tech link: "On 2005 Chevrolet Silverado and GMC Sierra 2500/3500 Series Pickups equipped with the 11.5-inch ring gear rear axle assembly, the factory lubricant fill level may appear lower than the published specification. This axle can be identified by the location of the fill plug on the rear axle housing cover, instead of on the front of the axle housing."



My question:
I have an 04 K2500HD with D-Max/Allison/limited slip, and the fill plug is on the front of the axle housing, so what size rear diff do I have, and the second question is should it be filled to overflowing, or follow the directions for the 11.5" ring gear rear axle, which says to put in 3 ltr of synthetic SAE 75W-90 gear oil?

hdmax, The 4.11:1 gearing is available for gasser. Not sure if it's limited to the Allison though.

I may be wrong, (But I don't think so!) There is just one differential that comes with the Duramax/Allison, or 8.1L Gas/Allison, or Duramax/6 speed, or 8.1L gas/6 speed combo. It is the 11.5" 3.73:1 American Axle. This axle is in both the 2500HD and the 3500 trucks equiped with the combo`s I listed above.

The 2500HD with the 6.0L gas/ 4 speed auto has the smaller ring gear differential. (I think it is either a 10.5" or 9.5") I am not sure about the 3500 with the 6.0L gas engine, or if it is even standard on that truck.
I had an '01 - 8.1L Gas/Allison with the 4:10 rear end. Pulled great, ate fuel like mad.