russelln

I have a 2008 GMC Sierra SLT 1500 with the Max Tow package - 6.0, 4L70 trans 4WD I have been changing all the oils but I am unsure what to put in the front axle. The manual says: Front Axle (1500 Series) Four-Wheel Drive use SAE 80W-90 Axle Lubricant or Front Axle (1500 HD, 1500 AWD, 2500HD & 3500 Series) use SAE 75W-90 Synthetic Axle Lubricant I suspect the first is the likely one but I am unsure as the rear axle takes the later SAE75W-90 oil How do you tell for sure? As I live in New Zealand I can't just go to the dealer & ask. Thanks in advance Russell