Doc - Anybody? Front hubs '92 S10 Blazer 4x4

I just had both lower ball joints replaced and a front end alignment done on my '92 s10 Blazer. While it was on the rack I asked the mechanic, (my brother), if it was
true that when coming out of four wheel drive I had to back up 5 or so feet to allow the front hubs to unlock. He replied that it was necessary to do that to allow the self locking hubs to dis-engage. He also stated that my front hubs were not self locking, but were always locked whether or not I was in four wheel drive. As if it were a front wheel drive. In all my lurking in this group I have never heard of something like this. Can anyone explain this? The truck handles well and goes into and out of four wheel drive with no problems. Is this ok? Or should I be looking to get rid of it before something ges BANG?
Thanking you in advance for any insights.
N.M.W.B.A.o.O.
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On Sun, 11 Apr 2004 12:43:51 -0400, snipped-for-privacy@webtv.net (No Mail Will Be Answered or Opened) wrote:

your truck doesn't have mecanical automatic hubs, which require you to back up to disengage. your truck uses a vacuum actuated Central Axle Disconnect (CAD) system to decouple one axleshaft in the housing to keep the front driveshaft from spinning. since the CAD is in the housing and not at the wheel hub, the CV axles are always spinning with the wheels. this makes your brother half right.
your truck sounds like it's operating normally.
hth, Bret
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GM S Trucks use a sliding sleeve on the right axle to lock / unlock the axle. There are NO automatic hubs on them like the Fords used. That sleeve is moved by the large vacuum unit on the right inner fender that pulls a cable and moves the sleeve. No need to do anything other than MAYBE let off the gas when shifting in/out of 4WD just to allow the sleeve to slide easier.
--
Steve Williams


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My thanks to both Bret and Steve W. I haven't worked on a motor vehicle for almost 30 years and it's amazing how much I don't know. I think my brother was just explaining things in a way that he thought I would understand.
Again, Thank you both,
N.M.W.B.A.o.O.
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On Sun, 11 Apr 2004 17:15:51 -0400, snipped-for-privacy@webtv.net (No Mail Will Be Answered or Opened) wrote:

Those guys pretty much answered it. I was over that system with a mechanic once, fixing the switch to engage the front axle. There's a vacuum switch on the t-case that causes the vacuum to pull that actuator under the battery and engage the front axle when switched to 4WD, this switch is a common failure point in the system as an FYI.
The axle may not disengage immediately as was said, but it will. The one in my old truck usually wouldn't until you slowed down some. It would be good practice to drop the truck into 4HI once or twice a month, just to give the workings a little exercise. Of course, you only want to do this on a straightaway if you're on dry pavement.
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