TM-9-2350-311-20-2 Maintenance Manual Volume 2 for M109 Cab Download
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TM 9–2350–311–20–2 1–17 1–15 DIFFERENCES BETWEEN MODELS Most of the differences among components of M109A2 and M109A3 howitzers concern the M109A3 model. There are 103 differences in the cabs of the M109A3 vehicle population. Variations among M109A2 vehicles and differences between M109A2 and M109A3 vehicles are minimal. M109A4 howitzers have updated hydraulic and electrical components and an added NBC system. M109A5 howitzers have been updated from the M109A4 models. In addition to all M109A4 updates, the M109A5 model also modifies the M185 cannon assembly to an M284 cannon assembly and M178 mount to an M182 mount. The maintenance procedures in this manual will call the mechanic’s attention to any differences in cab components which will affect the mechanic’s performance of unit maintenance tasks. Where parts which must be removed or inspected differ significantly in appearance, a cutaway view will be used to show the alternate parts. Part differences not relevant to the unit mechanic will not be mentioned or pictured. Below are some examples of cab component differences important to the unit mechanic. Functional group and part Number of Variations How assemblies/parts differ 00 Protective shields, race ring 3 Shields mount on race differently. Some M109A3 howitzers do not have a turret shield behind the com- mander’s seat. 01 Bearing balls 2 Some vehicles have 212 bearing balls mounted on 106 race ring spacers; other vehicles have 213 bearing balls mounted on helical compression springs. 02 Cannon assembly, howitzer 2 M109A2/M109A3/M109A4 howit- zers have M185 cannon assembly with M35 firing mechanism. M109A5 howitzers have M284 cannon as- sembly with M49 firing mechanism. Cannon assemblies are similar in maintenance characteristics, but there are subtle differences in parts. Refer to TM 9–2350–311–24P–2 for specific part number changes. Carrier assembly on M284 cannon assembly has a spring-loaded plunger assembly. The plunger assembly on the M185 cannon assembly is not spring-loaded.