🚗 Classic Fault — Mercedes-Benz (1976–1985)
W123 rear axle differential oil low — bearing whine
💰 Estimated Repair Cost
$15 – $50 USD
Parts and labour estimate
🔧 Tools Required
SAE 90 hypoid gear oil, fill plug socket, drain container
📋 Overview
Rear axle differential oil level drops through minor seepage, causing bearing and gear whine particularly under acceleration.
🩺 Symptoms
Whining noise from rear under acceleration. Noise changes pitch when lifting throttle. Rear axle running hot.
🔍 Possible Causes
Leaking pinion seal. Leaking axle shaft seals. Long service interval without oil check.
🛠️ Diagnosis Steps
Check differential oil level via the fill plug on the side of the axle. Oil should be at the bottom of the fill hole.
✅ Most Confirmed Fix
Top up with SAE 90 hypoid EP gear oil to MB 235.2 specification. Replace any leaking seals found.
91% of users confirm this fix worked (14 reports)
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