The Mercedes-Benz "Group" system |
| The original factory identification system was inherited from car and
truck production, it dates back to sometime right after W.W.I. The first
system was all "alpha" based and parts books were organized in the
following order: |
| M | Motor (Motor) |
| Ku | Kupplung (Clutch) |
| G | Getriebe (Transmission/gear box) |
| V | Vordachse (Front axle) |
| H | Hinterachse (Rear Axle) |
| R | Rahmen (Frame) |
| F | Federung (Springs) |
| St | Stussdämpfer (Travel dampener, shock absorber) |
| B | Bremsen (Brakes) |
| L | Lenkung (Steering) |
| K | Kühle (Cooling) |
| KrA | Kraftstoffanlage (Fuel system) |
| E | Elektrische Ausrüstung (Electric system) |
| D | Druckluftanlage (Pneumatic item, trailer brakes, lift cylinder, air powered rear 3 point hitch) |
| Z | Zapfwellen (PTO’s) |
| A | Aufbau (Cab, body) |
| P | Pritsche (Rear platform) |
| You’ll find this format followed in all the early service manuals, etc.. In
the late 40’s they realized that an all numeric system would be better
for the parts identification system, however, it took them awhile to
finalize the system. The motors were numbered: |
| 1 | Engine, non moving parts |
| 3 | Engine moving parts |
| 5 | Engine timing |
| 7 | Injection system |
| 9 | Fuel and air filters, etc. |
| 13 | Air compressor |
| 15 | Engine electrical system |
| 18 | Engine lubrication |
| 20 | Engine cooling system |
| 22 | Motor mounts |
This system has basically remained in place right through current
production.
Unfortunately, they first decided that each system, motor, chassis and
cab, would have it’s own number sequence. Thus chassis were first
numbered: |
| 1 | Front axle |
| 2 | Rear axle |
| 3 | Frame |
| 4 | Wheels/tires |
| 5 | Springs, shocks, dampener |
| 8 | Steering |
| 12 | Brakes |
| 13 | Transmission/PTO’s |
| 15 | PTO shafts |
| 18 | Bumper |
| 21 | Trailer hitch, fixed drawbar |
| 22 | 3 point hitch |
| 31 | Fuel system |
| 40 | Radiator |
| 62 | Battery box, wiring harnesses, etc. |
| In the early 60’s it seemed to the parts guys that this was cumbersome as
you could have a spare part with a group 3 number, but without looking
at it, you could not tell if it was an engine part or a chassis part. At the
same time MB was adopting key punch based computing systems and
they needed to standardize their part numbering sequence. Thus was
born the system used today, where the group number immediately
identifies where on a vehicle the part goes. The part number identifies
the group a part belongs to. The modern group system is formatted: |
Groups 01 to 23 are engine related |
| Groups 24 to 58 are the chassis including the platform |
Groups 60 to 92 are cab related
|
| The MB number system then tells you where something goes, and
whether or not it is a proprietary item or a trade item. The current front
brake caliper, that would fit the disc brake U900, U1100, U1200, U1400,
etc. in the forward, right hand, front axle position is now part number: |
A 427 421 20 98
|
| This can be broken down as follows: the "A" indicates it is a regular
Mercedes-Benz part. The 427 is the model this part was first used on and
also indicates it is a proprietary part. The "421" indicates it is part of the
brake system, and further more is a hydraulic component rather than
pneumatic which would use a "43x" in this position. "20" indicates this is
the twentieth version of this part, the "98" is the "part number" in the
master listing. The ninety eighth part. |
To really keep the parts guys confused, the inventory system is organized
to read this part number and stock it using the following sequence
numerically. Digit order: |
four, five, six, nine, ten, one, two, three, seven, eight.
|
| This system is why computer programmers, HATE MB’s parts system. It
takes some special software to teach a computer to count out of
sequence. Even though this caliper is built by ATE (Alfred Teves) it is
proprietary to MB. If it was an adapted off the shelf item, available
through the after market, the part number would start with zero such as
A 002 421 xx xx. The zero in position one, one & two, or one , two and
three, indicates the part is a common trade part. |
| A similar system is followed with part numbers for DIN (Deutsche
Industrial Normal) hardware items. These items are all in a 12 digit part
number form and are preceded by the letter "N": |
N 000960 020078
|
| This follows a similar concept. The "N" indicates it is "normal" hardware.
The "000" means it’s a standard item, the "960" means that it conforms
to DIN standard 960, which is a hex head, cap screw, with partial
threaded shank, the "020" is the diameter 20.0 mm, and the "078" is MB’s
designation meaning this is the seventy eighth 20.0 mm bolt, and
specification number 78 will spell out length, thread pitch, hardness etc.
In this case it is a steel, grade 10.9 bolt, M20 x 1.5 x 85 long and used on
the front shock mount on a 419 Unimog, and late model, disc brake,
U900, U1100 models. They follow this system with all of the hardware,
clamps, etc. that are trade items. If it is a specialty fastener they will give
it a proprietary MB number. A good example would be the differential
used in the U900, U110, U1200. The differential case is held to the ring
gear with eight bolts. Four of these are a standard DIN fastener and have
the part number N 000960 012277, a 12.0 mm bolt conforming to DIN 960.
The other four are a special "fitted" bolt, with a special diameter shank,
these have a MB Number A 416 990 52 19 since they cannot be
purchased from a bolt supplier. |
| All MB part numbers start with an alpha character. Unimog owners will
encounter: |
| A | A regular MB part |
| C | A newer designation for whole MB assemblies |
| N | A DIN hardware item |
| W | A special tool |
| This information is provided in hopes of helping an owner understand the part number a little better. |
-by Jack Russell
|
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