Looks like your driveshaft is not properly "set" (to me it looks like it is about to come apart - I would have to climb underneath mine to compare). I don't think you should have that much of the splined shaft showing.
I would recommend taking the driveshaft out, pulling it apart (make sure you mark it) and seeing how badly worn the splined shaft is - otherwise you may be able to loosen the big nut and pull the shaft back over the splined section.

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Jim