RAM CHASSIS CAB 2015 Owner's Manual page 522

520 MAINTAINING YOUR VEHICLE
When checking the fluid level (4500/5500 only), the
vehicle should be in a level position. The fluid level
should be ¼ in ± ¼ in (6.4 mm ± 6.4 mm) below the fill
hole on the front axle. The fluid level should be level with
the bottom of the fill hole on the rear axle.
Drain And Refill
On 4500/5500 vehicles, remove the lower bolt to drain
the axle fluid.
1 — 4500/5500 Rear Axle Fluid Fill Plug
2 — 4500/5500 Rear Axle Fluid Drain Plug
Refer to the "Maintenance Schedule" for the proper
maintenance intervals.