Mercedes-Benz E-Class W212 3.27 axle gear (big gear) refers to the final drive ring gear located inside the rear differential assembly.

Description:

• Vehicle: Mercedes-Benz E-Class W212 (varies by model, typically E250, E300, E350 depending on market)
• Gear ratio: 3.27 (meaning the driveshaft turns 3.27 times for each rotation of the rear wheels)
• Part type: Large ring gear (also called crown wheel) — main gear in the differential that meshes with the pinion gear
• Material: High-strength forged steel, precision machined and heat-treated for durability
• Function: Transfers torque from the pinion gear (driven by the driveshaft) to the differential side gears, which then power the drive shafts and wheels
• Location: Inside the rear axle differential housing
• Typical setup: Works with the matching pinion gear; must be replaced as a matched set to maintain correct tooth contact and avoid noise/wear

If you want, I can also give you the full part number list for the W212 3.27 differential ring gear depending on model year and chassis code. Would you like me to pull that up?