04 CAT 257B final drive gear oil??

I can't find any info in the book or online about changing the gear oil in the drive motors. Local Cat dealer printed off pages for me with steps on how to change. I see no drain or fill plugs like the pictures in the print they gave me. I thought maybe they were accessible from the backside so I unsolved the track frame, slid it out enough to see behind the final drive but It looks different than their print our and I see no obvious drain or fill plugs. After reviewing their print out more, the picture looks like the B2 series. I have the old school original asv style B series. Can anyone help me out here, is there gear oil to change and how do I access the drain and fill. Thanks in advance!