I thought I recognized some similarities in wheel cylinders.. Also '38 were self energizing cable brakes. '39 went to juice. Locked up my '38s cable brakes on dry pavement a few times when deer jumped out. They were good brakes if kept adjusted once a year.

 

You are right GB, '39 was the first year for hydraulic brakes. I knew that, I was think of the first year for tonner when I typed '38. D
Did the '40 tonner have an open driveline like the big trucks, or was it closed until '42 like the 1/2 ton?

 

I have a trailer here made from a '39 tonner rear frame. It is enclosed. I'm guessing they stayed that way til '42 as that's the year the axle was widened by 2 1/2" as well. I'm guessing that Willowbilly's 40 tonner has been converted to open since it has 8 lug axles under it. Maybe he can clarify once he gets to Texas.

 

I think my axles are early 50s. They are just chained under the truck.

 

Sorry, my bad. Correct: the rears are 1.5-in.
BTW, I have (what I believe is a) 2-ton COE.

 

Ford went open drive on the 3/4 tons and Tonners in 1940. I have an open drive 3/4 ton rear axle from a 41 if someone needs hard parts (condition may not be great).