What is difference between 1310 and 1350 joints?

Size and strength. The 1310 series joint is what you would expect to find stock in most Jeep or small trucks. A 1350 series joint/shaft is what you might find in many full size trucks. While it's not 100% accurate, you could say that a 1310 is a "half ton" joint and a 1350 is a "one ton joint". 

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