Make sure the drive cups on the 2 speed transmission and the front differential are tight. If the drive cup is loose, you will lose power to the front wheels.

To test this, hold the rear tires stationary and rotate both front tires (in the same direction of course). If the center drive shaft going to the front differential is spinning, you need to tighten the drive cup on the 2 speed tranny (make sure you tighten the setscrew against the flat spot on the 2 speed outshaft).

If it isn't spinning, there's something wrong up front. Make sure the center drive cup (at the front diff case) is tight against the flat spot on the input shaft. If it is, check your front differential for damage.

Good luck.