Symptoms
No visible leak: the oil runs inside the drive-shaft tube and overfills the differential, while the gearbox runs low.
The fix, step by step
- Drain the gearbox and remove the spare.
- Disconnect the front diff-lock linkage, the boot over the ball housing, the shocks, the lower spring bolts, the drag link and the axle locating arm, then roll the front axle forward (one Rocky Mountain Moggers crew also separated the torque tube at the diff).
- Unbolt the driveshaft, unstake and remove the slotted nut, and pull the output flange; a gear puller or jacking bolts will be needed.
- Seat the new seal fully against the bearing snap ring, line up the oil holes in the flange and spline, and reassemble.
- Expedition Imports also has a video of the job.
Tools & part numbers
- Heavy jack stands
- gear puller or hardened jacking bolts
- socket spanner 401 589 00 07 00 or a pin punch
- bearing press
- gasket material.
Where to buy the parts
Transmission output seal, front (directional)Expedition Imports ↗Amazon ↗
Transmission output seal, rear (directional)Expedition Imports ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz Unimog 404 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.