This is borrowed from RMM web site:
The "L" in the model number in all Unimogs stands for longer frame. The additional length is all behind the rear axle. In the case of the two 1650's it's a 376 mm difference. The "standard" or short frame models are designed to be used with a full range of rear implements and such as PTO's and three point hitches, backhoes, etc. The longer frame models are designed for installation of fixed bodies and are not available with Rear PTO's, three point hitches, nor suitable for heavy rear mounted implements. A lot of people assume the "L" is an abbreviation for LKW or Lorry? Nope, it simply is the first letter of "lang", the German word for long.
There is some variation in how MB used the designation. For instance instead of the model U1700 L/38, they had, for a time, a model called "U 1700 LL" meaning long frame and longer wheelbase. They finally standardized on the current convention of all "L" models are wheelbase of 3250 mm except when designated with "/37, /38, etc.." (Of course they had to violate their own system when they built a few long wheelbase models with short frames.) Thus you have such as a "U2150 /38". Look Ma. No "L"
