Did ya index the VSS when you reinstalled it?
On the speedo gear, there is a number, usually between 28-40. On the VSS there are corresponding numbers there as well. When you reinstall the VSS into the t.case, place the area where the numbers match in the 6 o'clock position .
Example- your speedo gear it a "38" (# of teeth by the way), the VSS will have a series of numbers that may say 35-39. Install the 35-39 slot in the 6 o'clock position on the output housing of the transfer case.
Or...
Did ya forget the snap rings that hold the speedo drive in place on the output shaft of the case?