I've searched this and nobody seems to have this same problem. I've got a 97 blazer with electric shift on the fly 4x4. 4hi/4lo/2hi. When I'm driving and I need the 4x4, I press the button, Goes into 4x4 smooth as silk. Can't even hear it, except the transfer case whines a little bit and you can feel it in the front axle and steering. The problem occurs when you try to go back to 2hi. You press the 2hi button when your moving and the light on the switch illuminates but the front axle does not go back into 2hi unless you totally stop(big pain in the butt on the highway) or occassaionlly it "might" go back to 2hi, but not without a HUGE clunck involved! I have a new transfer case switch because I thought that would be it. It seems that the transfer case goes back to 2hi, just not the front axle. Am I right in thinking that I shouldn't have to stop to go back to 2hi? This has me stumped because it goes right into 4x4, just not back into 2hi while your moving.

 

On most on the fly, there is a vacume switch. You might want to make sure that there is supply going to that. On mine the Vacume line is missing. So once I get that fixed then I can get back to 2 instead of full time 4. On earlier models there was a cable.

forgot to add that the line goes to the front axle

 

Well, that's what's got me confused. It shifts into 4wheel drive, just not out of 4 wheel drive on the go.

 

I also have a 97 blazer with electric shift. Your thinking is correct, I can shift on the fly from 2hi to 4hi or back at any speed with no problem. The only time I need to slow(2-3mph) would be for 4lo.
Not sure whats going on there, but u may want to look at posting on do- it- yourself by hanr3. Good info on 4x4 operations.

 

Well for 4lo, I wouldnt switch into it even going 2-3mph. I dont think it will even work if your moving. You have to be in nuetral then switch into 4lo.

 

Your correct, you must be in neutral to switch to 4lo. But if I'm rolling a little it seems to slide in easier and the 4lo lite goes on steady, then u can switch into gear.

 

First off ...the 4lo thing it MUST be in Neutral to shift into or out of 4LO.....and you can be rolling up to 5MPH...like blazewest said it is a little easier on things and a little smoother if done when at a slight roll. The other thing...not going OUT of 4wd....either your vacuum switch on top of the t-case is sticking.(pretty common) or you have two different size of tires (or 2 very good tread and 2 very worn tread). This will cause all of the symptoms that you have...especially the long dis-engaugement time and a loud clunk in the front when it finally disengauges.

 

The t-case switch is new. The tires aren't neccassarily bad and the tread seems to be all worn about the same, but I do have some new tires that I'm getting put on on Tuesday after christmas. Maybe that's it? Would an alignment issue cause something like this also? I'm due for an alighnment but I didn't think this would be it. Now that I think about it, The Blazer does pull to the right....

 

When would you actually use 4low? I put it in 4low the other day just to see what it was like and it didnt seem like the blazer liked it to much??

 

it is basicaly for towing or where are your torgue is shown...if you do alot of rock crawlin or somethin that involves alot of power...this would be what 4lo is used for..