This section is NOT intended to be comprehensive.  Rather, it provides an overview of some of the types of mower decks available, their primary differences, and -- in general -- how to install, adjust and operate them.  Consult the specific operators manual for your particular tractor and mower deck for ANY specifics.  If you do not have the correct manual, you can usually obtain them from Simplicity's Publications Department or through your dealer network for tractors up to 30 years old.  

42" A-C #2025080.  This Allis-Chalmers operating instruction is for a very common 42" mower deck that was used on most B-series and equivalent Simplicity tractors.  (Other A-C models 2029933 and 2029958 share the same owners manual with this 202580, using the revised Form TM-7004A.) These are 6" deep, left-discharge decks, with 3 blades, with a "one-piece" deck skin.  

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    3-Piece Deck Design

The earliest type 42" decks (shown above) for Simplicity 700 and 725 tractors (MFR # 990190) or A-C B-1s (A-C MFR #2025009), were "3-piece" decks, where the 3 pieces of the deck shell bolted together.  This was changed to a one-piece design around 1964.  

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Slot and Sliding Shaft Belt Tension Adjust

Then, the next enhancement was a spring-loaded idler pulley that replaced the "slot and sliding shaft" belt tension adjustment (shown above).  For example, Simplicity MFR #990285 and #990407 were such 42" decks with a sliding shaft adjustment.  The deck described in these operating instructions has both those enhancements, and probably dates from about 1966 or 1967 (?). 

300-400 Series Decks. This Allis-Chalmers operators manual is dated 1973  It covers the shallow 42" and 48" right-discharge mower decks used on many of the Lexington- manufactured tractors, including the A-C 300 and 400 series, and some Homelites.  See the Homelite Section for more information about their similarities and differences.

Simplicity 885 & 886.  This Owner's Manual covers two Simplicity decks (42" and 48") that are representative of the later decks used on Allis-Chalmers 700-series and Simplicity 7000-series.  They are deep-style (6" above blades) left discharge decks, that evolved from the deep decks described above.