Have a 2003 ls 3 button 4x4 switch. I found d that the 4wd actuator under the battery tray was bad and replaced her. Afterward, I tested to see if I had 4 wheel drive. I put her in 4hi and felt the front skipping whe turning (yeah!!!). Same thing in 4 low. When I stopped to put it back in 2 wheel drive, the light for that lit up. I drove about 40 feet and felt a pop. Thought I broke something to checked under the blazer and everything looked fine. I tried 4hi again and it was fine but it wouldn't go back into 2wd unless I put it in reverse for about 5-10 feet. Then everything was fine.

It's my understanding that reverse shouldn't be needed to disengage the 4 wheel drive (but I could be wrong. Wouldn't be the first or last time for that). Tried shifting back into 2wd while stationary in drive and also while in neutral. Same issue with both. Could the switch on the transfer case with the vacuum lines be going out to cause this issue? It is it another issue?

Thanks for any assistance. Living in PA, I need 4wd and want this issue resolved before it makes things worse.

 

I've seen some saying, that sometimes they have to be in a slow motion to (dis)engange the 4WD, on steady it does not switch over. That pop You've heard is mechanical engagement of a front differential.

 

Mike.308,
Thanks for your reply. The pop was loud enough that I thought I broke a u-joint or broke something. I tried moving slowly forward after disengaging and the 3 button switch saying I was in 2wd but nothing. Still in 4wd. Only way I was able to get it to shift each time like it was suppose to was by backing up 5-10 feet. Then things were good.

 

You do not have too put it in reverse too switch from 4hi or 4low too get back into 2 hi. At least when your vehicle is working properly. That is all I can help you with but someone else will surely respond back too you that can help you out...

 

Go Chevy,
That's what I was thinking but dont know what to check or where to start to trouble shoot this issue.

 

My guess - you was on dry ground and or dry pavement while playing around with 4wd - by doing so you put the system in a bind and by backing 10 or so feet you released the bind on the system

 

I was thinking that it could be 1 of 2 different things.

1. The cable is binding up. May be dry or kinked somehow. I can move it by hand but not sure how smooth or easy it is suppose to move.
or
2. Is the vacuum switch on top of the transfer case is worn and leaking transmission fluid into the vacuum hose and wouldn't let the vacuum free up to completely release the actuator. There was some transmission fluid in the old actuator.

 

Do all 3 lights light up yellow on the dash of your 3 button 4x4 switch when you switch from 2hi ect? If not you simply may have a faulty push button switch... Long shot I guess but who knows?

 

All that is inside the front diff. is a shaft with a gear. When U engage the 4wd the vaccum pulls a cable that moves the gear over the axle and the gears mess. When U disengage the 4wd a spring is supposed to let the gear slide on the shaft and the 4wd disengages, Sounds to me like there is some "gunk" a broken spring or a stuck cable not letting the gear slide back to the 2 wd position. My 4 wd quit working all together so I tore it apart and I could find nothing wrong inside. Reassembled it and it has worked great ever since. Don't know what else to tell you, just some thoughts.