Propeller Shaft
Are u talking about a cessna plane or a car?
please use easy language for a layman like me who has taken a panga by replying to this post I hope it wont backfire.
Its about size, old axles wont fit becoz Diesel Gear box are generaly bigger, i am telling u this based on my own diesel conversion expereince with Nissan Sunny 88.
Petrol axles were different, one was short and one was long. In case of rear wheel, its different story, usualy mechanics get a weld in the Propeller Shaft (as u would say) to bring it in line with the gear box and the rear differential.