241 -1/2 ton burb-havent used the 4 wheel [been using 2w]snce a heavy storm about a month ago -i lock the hubs,shift to 4 hgh,and i go-then as i drove [on very wet pavement]the front has a consistant vibe-so i take it out of 4 high-hubs still locked-and it goes away-could i just be low on tcase fluid?couldnt check cause of the rain....Thanks for any info-