4LO YES, BUT 4HI NO
 

Need help with my 4 wheel drive on my '93 GMC Jimmy with 153,0000 miles. It has the 4.3 motor.
Problem is that it won't engage into 4 wheel HI, It will engage in 4 wheel LO though. Where should I start to diagnos this problem. Nothing happens when I hit the switch on the dash. (4HI only). Please send help. Thanks.

RE: 4LO YES, BUT 4HI NO
 

I'm no expert by any means, but if it goes into 4lo, then all of the solenoids are probaly working and I would start by checking the 4hi button itself.

RE: 4LO YES, BUT 4HI NO
 

Check the vacuum actuator... I think it's under the battery, but might be in a different place on the 1st gen... Check a Haynes or Chiltons manual... Should be able to help locate it for ya.

RE: 4LO YES, BUT 4HI NO
 

Since I have 4LO working, wouldn't that mean the vacuem actuator is still good? Or do they work differently for each position?

RE: 4LO YES, BUT 4HI NO
 

I think that might depend on if your front wheels actually work or not...

I can't remember if the first gens had the option for the Auto function of the 4x4...