This Allis Chalmers Service Manual is a digitally enhanced reproduction of the original manufacturer-issued Shop Manual. This manual covers the H3 Crawler I-400 Backhoe Attachment (Crawler - I-400 Backhoe Attachment) | H4 Crawler I-400 Backhoe Attachment (Crawler - I-400 Backhoe Attachment) | HD3 Crawler I-400 Backhoe Attachment (Crawler - I-400 Backhoe Attachment) | I-400 Backhoe Attachment (For H-3 | HD-3 and H-4 Crawlers). Written in the language of a mechanic, it was initially given to the dealer's service department to provide enough detail for major repairs and complete overhauls. It discusses how to correctly take apart, repair, and reassemble your equipment. This is a vital guide if you are executing or thinking about extensive repairs or a full restoration. Even if you already own an original Service Manual that's in good shape, you will find our value-added content, such as post-publishing updates, corrections, serial number info and additional machine detail extremely useful.