Turned my 99 Blazer 4X4 on to 4hi (light is on) but no drive at front wheel. Jacked up front of truck wheels do not turn. Did anybody have the same problem? What could cause the 4hi light to be on but no power to the wheels? Thanks for any help you can give me.

233 or 236 Transfer case? Do you have the Auto 4W button?

Was the front drive shaft locked in or turning?
Is the right front axel locking in?
Be carefull just jacking one end up to test.
MT

If the lights in the switch are not blinking, the TCCM is not recognizing any problems. With all of the self test features built into the TCCM, about the only thing it could be is the clutch gear on the right front axle is not engaging. The actuator is moving the shift fork in the front differential and activating the switch telling the TCCM that the axle is engaged, or the lights would blink. An easy way to tell if the axle is locked, is with the engine idling, transmission in park, engage 4HI, then jack up only the right front wheel. If the wheel spins, the clutch gear is not engaged. If the wheel does not spin, the axle is engaged. Post your results.

Jacked up right side,started Blazer and put in 4hi. I could spin wheel. I could hear it engaging and disengaging when going from 2 to 4hi and back.

The right axle is not engaging. The clutch mechanism is operated by a vacuum actuator, located under the battery, that pulls a cable that is attached to the right axle tube. Inside the axle tube there is a shift fork that moves the clutch gear and engages it to the clutch shaft. When it moves the clutch gear, it activates a switch, (right next to where the cable goes in), that tells the TCCM that the axle is engaged. The TCCM has no way to monitor if the axle actually engages. The problem is in the clutch gear/clutch shaft. The axle tube needs to be removed to access the mechanism to repair it. I think the noise you were hearing when switching from 2WD to 4WD was the encoder motor shifting the transfer case. Here is a link that shows the front axle: http://img413.imageshack.us/my.php?image=frontdifferentialxw4.jpg