i just did an engine rebuild, and i'd like my odometer and spedo somewhat correct. i have a 91 with 4L60, and NP241. i'm assuming it has an electronic sensor?? i have 4.56 gears with 33" tires, so, yeah, my spedo is way off. when it says 85, i'm actually doing 65. can i not change the driven gear in the tcase? or do i have to fix it electronically??