Differences between a M931 and M931a

[marsman]

What are the differences between a M931 and M931a? I have been looking around and not having much luck. I have seen tires differences on some but not all. I have seen the super singles on older trucks and depot rebuilds and then again i have seen the smaller tires on both. I know the M931a2 has many upgrades. Any and all help would be great.

 

[M813rc]

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[marsman]

Sorry, I should have said mechanical differences.

 

[RIDDLE1]

The only difference between the 931 and 931A1 is that the A1 comes with the 14.00r20 super singles on combat wheels. Both have the same NHC-250 Cummins that is naturally aspirated.

The A2's all come with the super singles. The also have a more modern 8.3L Cummins that is turbocharged. Also, the A2 axles have a flat bottom vs the rounded bottom of the older trucks. That just helps increase the ground clearance. The A2 also has CTIS(Central Tire Inflation) which is truly junk in my book.

 

[marsman]

Riddle1,

Thanks so much for the information. I have been reading the teams without luck. Being a old avation mech, an "a" "b" or "c" ment most offten a number of updates. All I could finds was the tires and ABS. This is good stuff again thank you.

 

[maddawg308]

For all of the M939 series trucks, the differences between the straight version of whatever vehicle you have (M923, M925, M931, etc) and the A1 is mainly the super single tires. I was told there are a few other minor differences, but heck if I know what they are, must be REALLY minor. The A2 variants for any of the vehicles involve a new smaller Cummins engine, which made 240 hp (versus the previous NHC-250's 250 hp). All models used the same Allison tranny and 2 speed transfer case.