Symptoms
One or all locks won't engage, or drop out. It's usually the actuation, not the differentials. On a 2005 G 500 an MBWorld owner found the centre lock vacuum-operated and the front and rear locks hydraulic, and a 1997 G 320 owner notes the locker circuit uses brake fluid; confirm your truck's system in the factory manual.
The fix, step by step
- Check vacuum at the centre-lock hose on the transfer case, then trace back through the reservoir, hoses and switchover valves with a tee-in gauge.
- Split connectors and perished rubber fittings are common.
- For the axle locks, check the hydraulic lines and fluid.
- Change the diff and transfer-case fluids while you're in there.
Tools & part numbers
- Hand vacuum pump with gauge
- vacuum tees and line
- connectors
- brake-bleeding kit
- gear oil
Where to buy the parts
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz Europa International Gs 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.