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Rear axle "tow" rating not GAWR

2663 Views 6 Replies 6 Participants Last post by  ykdave, 
2500 Grunt
Do Chrysler engineers use a formula or a value or rating for determining the shear or tensile stress on our rear axle or 5th wheel hitch? I know that there isn't a practical way of users to determine what it is but...Everything that is talked about with specs is just load or vertical load? If I have a 17000# toy hauler fully loaded and have a 1400# plus sandrail behind the 3 axles then my pin weight might be within the 6000# GAWR of the truck (6000#- rear axle truck dry scale weight) because of the location of the sandrail load but what about the pull or tow weight of the load/toy hauler? Or do you assume that my 6000#GAWR vertical load of the truck is the weak factor. In other words, can the internals of the rear axle or be over worked with a horizontal load before you hit the GAWR of 6000#. My father in law fried a bearing in his rear axle pulling a heavy toy hauler recently. Yes, he was over loaded and never had it on the scales but I am curious why horizontal load is never discussed or is it worked into the vertical load specs? Or am I just missing something??
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STONR
I don't know of any horizontal load specs. I would start measuring differential temperature. The more load/power you apply to the axle, the hotter it will get. You could pull a super heavy load at a slow speed (like the Toyota pulling the space shuttle), or a lighter load at a higher speed (real world tow weights) and end up with the same differential temperature.

With the amount of power that our trucks have (and are capable of making), followed up by a heavy trailer (not just pin/hitch weight but gross trailer weight), factor in wind resistance and hills/gravity... You could cook the gear lube. This is why the new 800ft-lb Max Tow Dodge came with a different differential cover with cooling fins.

The weakest link is the u joints, or loss of traction.
The weakest link long-term I think is heat.
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