Suggestions for cleaning exterior of 4spd

i dont know if water will get in or not. but if you live near a blue beacon truck wash place they have a acid wash for alum,,doesnt hurt alum at all..will dull polished alum..go there on a rainy day and they can take there time..no one washes there big truck in the rain...its best to take all ur alum there at once..ie intakes old alum wheels. brackets etc..its gonna cost the same..ur probley looking at 30-40 bucks maybe less..or if you dont mind the mess theres always driveway cleaner..muratic acid. its a mild acid..good luck