The Stovebolt Site Forums The Shop Area Engine Shop Installing Patrick's 3.55 gears in 1938 axle

I looked at doing the same thing with my 39. I spoke to Patrick about it. He is indeed a great guy and believed it could be done but appeared uncertain about the details. I had a 41 differential available and started comparing it with my 39 and found at least two issues.
1. Axle housing has the differential opening shifted ½” to the left on the 41. This is reflected in the different lengths of the 41 axles (the left is shorter than the right). On the 39, they are the same length. If you used the 41 pumpkin in the 39, your torque tube would be off center by ½”.
2. Propeller shaft and torque tube were different lengths. You would need to modify toque tube and propeller shaft and use different u-joints.
Given these and other difficulties, I have for now, not attempted the conversion. It would seem to make more sense to swap in a complete modified 40-46 differential. This would still require modification of the torque tube/propeller shaft. I could not easily do this with the 41 I had. It is from a ½ ton and my 39 is a ¾ ton. They have different axle housing diameter and spring placement. I would also like to hear from anyone who succeeded in the conversion and the issues they addressed. There are probably other things that I have over looked.