Well I am going with the 5:43 gears so save on RPM........ HOWEVER........... my intentions were to convert the rear to an open drive shaft, mainly for ease of parts and familiarity, b...u...t... the more I read the more I realize that I am playing with the design geometry of the 1940 torque tube ...... changing to an open drive line seems easy until you read.....
Will my 1940 rear springs and in particular spring hangers handle the axle wrap up......? and I am not going to drag with the 235 engine I plan to install.
I could even change the whole axle open style from a similar era Chev that I have. From what I have read in the various GM parts manuals the axle casting number was the same for up to 3 tons onthe Canadian Military Pattern trucks....and by the way they were all open drive lines back to the early models designed from off the shelf parts in late 38-39. The early model were huge cast iron contraption with extra beefed up ribs but then they quickly adopted the more simple cast steel design and made millions of them.
At first I was hoping to use the 2 speed axle but the ration is low and lower with 8.1 for the low range.
I have seen in junk yards trucks with a second transmission and one model used an over or under drive bolted between the tranny and the bell housing.....simple lever hi neutral low...... then the GM 4 speed. They all looked dealer or after market installed and mainly on logging trucks used at low speed.
Has anybody done the drive line conversion only and what was the end results???? pitfalls to avoid????
Thanks
Bob C
