Obviously we understand viscosity and temperature choices but, actually never knew a gear box could live (debatable in some threads) with ATF but it makes sense if you live in cold climates. After reading I got comfortable with what Mopar recommended since I live in Az., - GS4 spec 85-90 I found Sta Lube GS4 85-90 at NAPA and Amazon $32 for a gallon on Amazon lands today...well maybe, isn't that another rabbit hole? ha ha ha Are you in cold climate?