I wonder what the expansion rate is for each inch of axle length is? Where's Bob when ya need him
@RJRENTON lol
The biggest factor is: The axle's alloy, such as a chrome-molly steel....Stock axles are typically made of
medium-carbon 1039, 1050, or 1055 alloys, and in some cases 1541 series steel that is forged and heat-treated or hardened.
What is the difference between 4140 and 4340 axle shafts?
However,
4340 has more carbon, while 4140 has more chromium. One of the most significant differences between the two metals is the inclusion of nickel in 4340 steel, which accounts for the metal's greater strength and fracture toughness.
Typically, steel is rated by the SAE or the ASM according to its particular elements. Proven and standardized “recipes” are issued a four-digit number. The first two signify the steel group, i.e. carbon steel, nickel-chromium-molybdenum steel, etc. The second two indicate the carbon content in hundredths of a percent, which is variable according to end use.
10XX, 11XX, 12XX, 15XX = The carbon steel group. Most standard OEM axles are 1040 grade. OEM axles are generally heat treated to 40 Rockwell in the center with the outer layer at 55-60 Rockwell to a depth of about .180 inch. These grades all carry from 1.00-1.65% manganese. The industry differentiates these steels by their carbon content, i.e., “low carbon” and “high carbon” steels. The last two digits “XX” indicate the carbon content of the steel. A “30” indicates 3% carbon, “40” indicates 4% carbon, and so on.
13XX = This manganese steel group contains 1.45-2.05% manganese. If it contains 1.6-2.05% manganese, it can be called an alloy steel. This grade is used by aftermarket axle builders because the high manganese content allows for more flexibility during the heat treating process. Some 15XX steels have 1.6-2.05% manganese.
41XX, 43XX, 47XX, 86XX = The nickel chromium-molybdenum group. An alloy containing .65-.95% chromium, .2-.3% molybdenum and 1.55-2.0% nickel. Chromium increases hardness and the elastic limits (when the material is quenched), as well as increasing corrosion resistance. Molybdenum and nickel also increase hardness.
The other influencing factor is temperature. The material will grow, lengthwise, but also on the diameter to a lesser extent. This is called Coefficient of Linear Expansion. Not knowing the axle 's alloy, its length and the max temperature involved, one could ASSUME an overall length growth of say, 0.003" - 0.005", which would be handled by the 0.008" suggested by the FSM for the Timken tapered bearing installation. Where as with the other brand of axle bearings, 0.005" preload will likely cause a bearing failure over time, plus the normal axial loads imposed due to cornering forces.
Not sure if this answers your question.....
BOB RENTON
