Daewoo Musso fault

How about friends:
The fault is the SGTE: it turns out that the truck does not exceed 50 kms/hr
the engine is without problems is as if the traction had been stuck (4x4), so we reviewed the system the control selectors (4Le, 4 high and 2), but the system works normally, bone in 2 only hook rear axle and when selecting 4x4 it hooks 4x4. Truck is without connected front traction but the output ratio of the rear cardan box is very slow.
?????????
Some
thanksgiving