Symptoms
One or all locks refuse to engage or drop out. On mid-2000s W463s the centre lock is vacuum-operated and the axle locks hydraulic, so one vacuum leak can disable the whole sequence.
The fix, step by step
- Confirm vacuum at the transfer-case hose, then work back through the pump, reservoir and switchover valve block with a tee-in gauge.
- One 2005 owner's fault was a split plastic connector inside a rubber Y-fitting under the brake booster.
- Bleed the hydraulic lines and change the fluids while you're there.
Tools & part numbers
- Hand vacuum pump with gauge
- vacuum tees and line
- connectors
- diff and transfer-case fluid
- bleeding kit
Where to buy the parts
Lisle 20300 vacuum gauge / pump testerFCP Euro ↗Amazon ↗
Genuine Mercedes vacuum hose connector 117 078 03 81FCP Euro ↗Amazon ↗
Genuine Mercedes vacuum hose 000 158 14 35FCP Euro ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz G 55 AMG 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.