5 ton developmen history

[ST Dog]

Anyone here got links to good info on the history of development on these trucks?

Particularly the evolution of the M939.

For example, I've read that the M939 was a Product Improvement Package upgrade from the M809.

Were initial M939s new production or the result of RESET mods to existing M809s (like is done with aircraft)?

Any history as for the whys behind the changes between the M809 and M939?

 

[WILDBOY6X6]

HI The basic and A1 M939's are the same as the M809's only big diff is the 939's have an auto trans and some electric valves etc on engine, and a1 has single tires.
The body is new (only the cab shell wind shields and hood) the rest is the same as the 809's too,both still use the NHC-250 cummins eng the a2 939 is an 8.3 ltr.
The radiator and fan are diff too,but not a lot else other than the a2's have CTIS tire system so hubs are diff, also all 939's have air brakes not air air over hyd.
The battries are under pass seat instead of under r/s cab door. They are new units not rebuilds however just more gov waste since as I listed above they are mostly the same
so they could have done rebuilds and saved some of our tax $$ hehe. Well but then we would not have had as many 809's to buy now hehe.

Steve

 

[ST Dog]

So the frame is identical? I though the new truck was wider.
The differentials? Transfer case?

I wonder how much really could have been reused from an M809 in a RESET/upgrade program.
And would the disassembly and inspection of those parts really have yielded any savings over a new build

How about some whys?
Why air brakes instead of air-over-hydraulic?
Why the increased height?