Your ratio is 4.27, they made the gears taller to help with emissions. These trucks also were the first sportronic transmission type, it is supposed to learn how you drive and adjust accordingly but it doesn't work very well with the 4.27?s even on stock tires. 3.5?s are also high RPM engines so really if you had 31's and 4.90?s the truck would be really happy.

1999 Montero SAS'd on Kings and stuff

1998 Montero trying to get a V8 Swapped