no 4wd on me sporty


hello and happy christmas, i wonder if anyone could help me please.
i have a '94 sportrak and there is no drive going to the front prop. i have taken out the oil check bung on the transfer box and the drive chain is intact and turns with the front prop.
hi/low ratios are working so i assume that its something to do with where ever the chain gets the drive from the rear prop, any idears before i take to a dealer?
also it would be very handy if anyone could supply a diagram of the transfer box so i can have an idear of what is going on, i am getting a cd-rom workshop manual but dont hold much hope as to whether it has any good diagrams.

all the best and thanks for any help, mark