Not terribly familiar with the automatic t-case setup, but if it is directly shifted with a shifter into the top of the case, then it should shift in and out of 4WD any time. If there is some vacuum actuated part of the shift linkage, then inspect that for leaks. If directly shifted, the 4WD light says that the 2WD/4WD shift rail has moved far enough to actuate the switch and turn the light on. If Hi/Lo range also works then the shifter is in properly, if not it may be just stabbed into the 2/4 shift rail.

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
4Crawler OffRoad - 4x4Wire discount code