4x4 3:73 can i go lower

[peglegs]

i recently purchased this 87 1/2 t. 4x4 305 cu automatic when doing a rear brake job i noticed a lot of play turning the tire b/4 the opposite tire moved so that in conjunctuion with a clunk when shifting in reverse the mechanic says he sure its the spider gears? in any case they are 3:73 would i be ok with a lower gear ratio rear end. dont plan on doin to much with the 4x4 only a few muddy roads/hills or rocky logging roads occasionally. its less expensive to replace the rear than have it repaired & do a little better on gas milage thank you.