Ideally, it should be 2-6" ahead of the rear axle
That being said, I have a 6.5' bed and had still had to lengthen the trailer hitch to be able to turn 90* with the fifth wheel hitch properly mounted in the truck, and not hit the cab. There are slider hitches available for fifth wheels, but I didn't want to use one.
My hitch is 3" ahead of the rear axle
, I believe.
The other big benefit of lengthening the trailer hitch is that I can open and close the tailgate while hitched up now.
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