I just changed my 5600 lube at 100k. first put in amsoil ATF, worked great. Was told by my fellow TDR members to get the ATF outta there and put amsoil 5-30. . I did so and now have a screaming case of gear clash while up and down shifting until the transmission heats up. I know it calls for the syncromesh stuff, but thought i'd try a synthetic product. Any suggestions? Is the ATF really bad for it? also, why is ATF ok in the transfer case, but not rear/front end? is there a difference in the gearing, besided the LSD? Jus wandering. Lee