Mercedes M-Class Diff Locks
One can modify a ML transfer case by adding a mechanical lever which
locks the planetary gear set between front and rear axles.
Plenty of inexpensive used transfer cases are available from sources
like Potomac German Auto and MBATC. One could also use a transfer
case with progressive electrical motor driven lockers, and tie it into
the traction management.
Click on picture to look inside.
When the orange planetary (8) is locked, the yellow output shaft (3) runs at the same speed as the green upper drive sprocket (9). Simply welding them together works, but that's a bit too permanent for some folks ;-) A better solution is to mill claws into (3) and (9) and to shift them into locked and open positions.
One can also connect (3) and (9) with a clutch, activated with a
shift fork, as shown in the inset. This allows locking even when
driving.
For rear and front lockers, one can exchange the open differentials with a used W124 4-matic center piece, which can be found for as little as $50 with some luck. And require some rework and modification. They use clutch packs to activate the locks. The old 4matic has a soso record for reliability, and an overhaul is not unusual, for any driveline with mechanical locks.
Team ORC modified these diff locks for their Racing ML:
An ML transfer case with differential locker is shown on the left. The locker valve
was installed between the normal low range actuation motor, a windshield
wiper motor, and the rear drive flange. The center piece on the right
is similar to a W124 4-matic's.
part numbers
163 280 06 00 M-Class transfer case
163 280 08 00 M-Class transfer case, ML320, ML430 2001-2003
163 xxx xx xx M-Class rear axle center piece
124 350 22 03 W124 4-matic rear axle center piece, 3.27:1
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