I would like to have information chart on cat d6B and D5B serial # and horsepower and start and end serial # on 44A and 25x and wide gauge. Thanks 
Farmerd5

Total production of the D6B 44A was 13,071. Start S/N was 44A 1.
Craig

   

D6B 44A 1 thru 44A  284 were 1959 production. All of my manuals list 44A 1 as the starting S/N. The original owner of my D6B 44A 2546 told me he bought it new in 1960, the list shows it to be a 1961. 
Craig

Hi Neil,
I don't know about the year model Caterpillar uses compared to S/N. Bruce Oz's list shows the D6B production started in 1960 at S/N 44A 285. I haven't taken the time to dig through my library, but I remember the D6B was available in 1959 starting with S/N 44A 1. His list shows a HP increase at S/N 44A  3876 but my part books show a big difference at 44A 6857; again, I'm not sure which is correct.
Craig  





 

I have the same s/n source book that Bruce Oz is referencing and it is full of errors and not a reliable source of information.