I'm running a 54 front axle under my 37. No problems. The Chevrolet part number for the front axle is a cast number that they started using in 41 and goes through 54. The difference may have to do with steering issues because even though they use the same axle, the steering is set up differently with 41-46 using one kind of box and 47 and up another. I'm using a 41-46 box on my truck. A 47-54 box will not work on my truck, but, again the axle is the same.
