Well, I have the 6 speed, but at the end of May this year when I had my new South Bend Con FE clutch installed, the guy who did the job replaced the ATF in my 4x4 transfer case with Amsoil synthetic ATF. I inspect my truck usually every weekend for drips, leaks and any other visible problem, and now with 2 months and maybe 5,000 miles since the Amsoil went in, I see no evidence of leaks on my transfer case.
Tom