PeachParts Mercedes-Benz Forum - View Single Post - got my g in the dirt today. The rear and front differential lock are not engaging.

DUTCH · #2 11-06-2009, 06:44 AM

The lockers can be engaged while moving. The center diff lock is vacuum operated only.

The front and rear are a combination of vacuum hydraulic. The vacuum operates an intensifier that uses hydraulics (brake fluid in a separate reservoir) to lock each diff. The front will not activate until the rear is fully locked (red light).

Have you bled the diff locks? It's done just like the brakes. The bleed screws are on the diff lock slaves which are mounted on the back side of each axle.

The first place I would look is to check the fluid level. There's a small reservoir in the engine bay in front of the driver. It's usually mounted on the inner fenderwell right next to the firewall. After that I would check the vacuum lines, and then the intensifiers themselves. They have been known to go out.

Lastly, it's possible that the rear diff lock slave has locked up with crap inside. This would require disassembly and a possible rebuild or replacement.

I've attached a schematic of the system and the WIS procedure to bleed it.