* Transfer Case Issues: This is the most common problem. The transfer case selector motor or linkage might be malfunctioning, preventing it from shifting into high range. There could also be internal problems within the transfer case itself, such as a broken shift fork or worn components. Low range often works because it's a more mechanically simpler engagement.
* Vacuum System Problems (if applicable): Some 1994 Blazers used a vacuum system to control the 4WD. A leak in the vacuum lines, a faulty vacuum solenoid, or a problem with the vacuum pump can prevent the high-range engagement.
* Electrical Issues (if applicable): If your Blazer has an electronically controlled transfer case, a faulty switch, wiring harness, or even a blown fuse could be the culprit.
* Shift Linkage: A mechanical linkage connecting the transfer case shifter to the transfer case itself could be bent, broken, or out of adjustment.
* Fluid Level/Condition: Low or dirty transfer case fluid can affect shifting. Check the fluid level and condition; replace if necessary.
* Actuator Problems: Some systems utilize an actuator to mechanically engage the transfer case. A faulty actuator can prevent engagement in high range.
What you should do:
1. Check the owner's manual: It should have a troubleshooting section or a diagram of the 4WD system.
2. Check the transfer case fluid: Make sure the fluid level is correct and the fluid is clean.
3. Inspect the vacuum lines (if applicable): Look for any cracks, leaks, or disconnections.
4. Check fuses and relays: Check the fuses and relays related to the 4WD system.
5. Inspect the linkage: Visually inspect the shift linkage for damage or misalignment.
6. Test the 4WD switch: Make sure the switch is functioning properly. A multimeter might help.
7. Consult a mechanic: If you're not comfortable troubleshooting these components yourself, take your Blazer to a qualified mechanic specializing in 4WD systems. They have the tools and expertise to diagnose the problem accurately. Mentioning the specific symptoms ("only works in low range") will help them narrow down the possibilities.
Ignoring the problem could lead to further damage to your transfer case. Proper diagnosis and repair are essential.
