Hey Cliff, to go to an axle that has a larger diameter than the 2-3/8 inch 3,500 lb axle you have on your trailer currently you'd have to go to a 3 inch diameter axle which would be between 5,200 and 7,000 lb. This will definitely require a new hub and bearing setup as the spindle size is different but you could keep the leaf springs you have now. view full answer...