i have a 1990 f150 4x4 5.8 e4od trans with 35 in tires. has 3.55 gears. what speeds should it shift at when stock tires are on it and driving normal? i get 15,25,35 and then 45 but speedo hasnt been calibrated with new gear yet. does speed,mlps or tps determine shift speeds? or what does? reason im asking is it shifts fine was rebuilt a year ago . it will down shift and upshift when im at 35 but if i stay above it its fine same at 45. down then up unless i run over 45. no od light flashing at all and no codes.if i switch the teeth gear at transfer case would i need a 16 tooth gear? i think i have a 19 now.any help or ideas guys would be great. thanks