Auto Parts: Reverse is lagging, 4wd system, gmc jimmy

Question
Ok, I have a 96 GMC Jimmy. 4x4, at, push button 4x4, i'm having probs with the 4x4, but besides that, when i shift into reverse, sometimes it won't engage entirely. I give it gas in reverse, it slips a little, then THUNK right in to reverse. But back to the 4x4, i switch to 4-hi or 4-lo and the brand new selector switch blinks (both 4-hi, and 4-lo) 3 times and then ? is it 4x4? i don't know, and then its a pain in the butt to get back out of 4x4. I just spent a good amount of money on this Jimmy, so i don't have much more to spare right now so a shop is out of the question. any help will be greatly appreciated.
Russell from Mo

Answer
Hi Russell,

Your vehicle IS a shift-on-the-fly, but it was 'new' technology when yours was made. I've had the same issues with my 4WD also as I have a 96 Blazer 4X4. I will assume you recently purchased this vehicle and are unfamiliar with 4WD systems operation.

Your 4WD actuator is vacuum, so you do need to give it a few seconds to fully engage the front axle once energized, which is why you're getting a 'clunk' when you begin to move. The three blinks the 4WD light is giving you is telling you that the 4WD is failing to engage because you are in a forward or reverse gear and stopped. While stopped, you need to be in NEUTRAL to shift into and out of 4WD modes. NEVER SHIFT INTO 4-LOW WHILE MOVING! Shifting from 2-High to 4-High and visa-versa while moving UNDER 40MPH is fine, but you should ALWAYS be completely STOPPED and in Neutral to shift into LOW range.

So it sounds to me like your 4WD system is working properly. Follow the procedures above when you engage or disengage your 4WD system and you shouldn't have any more problems.

Thanks for the question, I hope this information was helpful to you.
Fred
www.knucklebusters.us
570-453-0910
"Re-use is the best form of recycling" Help us recycle by purchasing used parts from us!
Looking for an ASE Certified shop near you? ASE Certified Technicians are the BEST of the BEST!
Click here: http://www.ase.com/bluesealsearch/locator.php