Symptoms
The centre or rear lock won't engage, or engages and drops out. On W463s the fault is usually in the vacuum supply, not the differential.
The fix, step by step
- Check for vacuum where the lines meet the actuators, then work back through the reservoir, hoses and switchover valves, teeing in a gauge on each section.
- Owners regularly find split connectors or perished rubber fittings.
- Remember the 500 GE has no front lock, so there's nothing to fix there.
Tools & part numbers
- Hand vacuum pump with gauge
- vacuum tees and line
- replacement connectors
Where to buy the parts
Lisle 20300 vacuum gauge / pump testerFCP Euro ↗Amazon ↗
Genuine Mercedes vacuum hose 000 158 14 35FCP Euro ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz 500 GE V8 parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.