UNIMOG Colorado
Rocky Mountain Moggers

The Mecedes Benz part numbering system.

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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Copyright © 2003 Last modified Saturday, February 05, 2005 01:12:58
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