[David_Hayward (RIP)]

Apart from seeming to settle the argument about the rating of the Gun Tractors, we may also have the means of settling the argument as to which CMP came first: F15A or GT/F8/F30S/F60S/F60L.

As Tony says the F15A [not sure what was fitted to the C15A!!] had a 1:1 transfer case, whereas all the others had a 'two-speed auxiliary transmission', with the PTO for a winch. The F-GT clearly differed from the F15A as we have discussed previously. It does seem that save for the evidence of the 30-cwt rating for the 2-pounder Chevrolet Portees, the GTs were officially rated by the DND in Ottawa as 60-cwt. chassis.

Two thoughts arise therefrom:
1. Why did the F15A have a different transfer case design from the GT save for the fact that no winch was required? and
2. Is there any relationship between the F15A and M-H case or 'the rest' and the M-H case?

Why I would like to know is because Sid Swallow created the prototype CMP as a 15-cwt. chassis because the 1938 and 1940 G/S 4 x 2 trucks that preceded were so rated, then he added 4 x 4 drive because the WD in London had changed Spec. 36 to delete 6 x 4 drive in favour of 4 x 4 for cross-country performance in 1939, and finally because he could lay his hands on proprietory components in the shape of Timken-design GM front axle and M-H components to mate with the Ford rear axle.

If the F15A used a M-H case then this proved it was the first-designed, and as the other multi-drives had/had to have a PTO facility they were developments. If it was the other way around then the production F15A owed nothing to the prototype and it was a matter of production/ component expediency..though the F15A is mentioned first in the handbook and the 'others' second.