No way on earth you were in 4lo doing 60... your RPM's would have been through the roof, whether your tach was working or not that engine would have been absolutly screaming to get you to that speed. When I hit the sand dunes around where I live I beat the living hell out of my transfercase by leaving it in 4lo flying through gears with my TF999 automatic... 3rd gear hiting 35 was quite a task and my engine wasn't quiet about the situation either.
Good news is my transfercase survived the day, bad news is, I still love to put what's left of my stock equipment to the test! Still running 36" tires, 3.07 gears, and 8+ inches of lift with my dana 35...
dont tell anyone around here that there is dana 35 has lasted 2+ years with no signs of failing, one fluid change, sand in the tubes, and pushing 36's.
... According to overwhelmingly bad repuation of the turdy5 it should have blown up the moment I put the jeep in drive after installing the lift and tires haha.