When switching into 4wd it seems to switch just fine, it sounds/feels a bit different, but when switching back it seems to take about 15 seconds and 30mph+ before i get a light clunk and its back in 2wd. Is this delay/clunk normal?

Sorry, this is my first vehicle with 4wd so I'm totally green on this

 

a delay is pretty normal and the clunk is the sound of ur trans case disengaging. its all normal.

 

Is there an easier way to tell that it did in fact go into 4wd? Right now i just hear a bit different noise when driving and it slows down faster, i'm assuming extra drag on the drivetrain

 

And another thing, the manual says I can switch into 4HI at any speed, but the guy I bought it from said it's easier on the tranny to be stopped and shift into neutral when switching. Any truth to this?

 

when you switch it into 4wd, get out of your truck, and try to spin the front drive shaft, if you can spin it, its not in 4wd, do the same when you disengage it, if it did engage, and you take it out of 4wd, and you get out and try to spin the front shaft, and it does not spin, it did not disengage

 

You can switch into 4h1 at any speed, on the fly 4wheel hi.
I personally dont do it above 25 or so
as for 4wheel low, That obviously needs to be while in neutral

 

15 seconds is too long. One, maybe two seconds, that is more normal.

 

If yours is a 3-button 4WD switch, try reading the TCCM codes, as described in the "4x4 no worky" thread in the DIY section.

 

X2. Before I fixed my vacuum lines and dash switch, it took forever to change modes, if it did it at all. Now I hit the 4x4 button and one blink later, it's on.

But if it's going into 4x4 fine and rather quickly, and it's having trouble coming out of 4 wheel, I'd probably start with the vacuum side of things, and the front axle actuator cable. On NV236, I'd disconnect the line going to the vac actuator for the front axle, engage 4x4, and disengage. See if the vacuum goes instatly to 0 or if it takes a while. Best way to do this would probably be a long length of hose coming from the hood into the cab through your window. Put your thumb over the end of the hose, and see if it cuts off instantly or if it's still trying to draw after you disengage 4x4 operation. It'll let you know if the vac solenoid is leaking or not.

On the other transfer cases, the vacuum switch on the transfer case has 3 lines that run to it. There is a possibility that one of the lines may have come off and is not allowing the plunger to operate correctly. (BTW, get the GM part for the switch if itself is bad; it's not worth the crawling around to do it again, in my opinion.)

But, also check the cable. All one needs to do is just simply pull it down with a vacuum pump to around 17" of vacuum. This just tests the ability of the actuator to hold vacuum. Then I pull the front of the plunger by hand to see how hard the cable pull is, and if there is sticking or binding. It'll take more force than you think, but it should be smooth, with no crunching, sticking, or grinding. Cable pulldown should be 1/2" to 3/4" (with reports indicate the more you have, the better, but that's somewhat discretionary.)

 

As stated previously, 15 seconds is not normal. It should engage/disengage within a second or two at most. I also agree that it could be the typical vacuum problem...however a "clunk" is also not normal. Something may not be meshing/releasing properly.

The manual is correct. These systems are designed to be shifted into and out of 4HI on the fly. As a side note, I have driven 4WD vehicles as my daily drivers for 25 years or so...Blazers, Durango, Jeep, Samurai, manual, automatic, etc. I have always shifted into and out of 4HI on the fly when the need required..even at highway speeds (50+mph)...and I live in the NE where the need is common during the winter. I have never damaged any of my 4WD components. Its always been a smooth transition (on slippery surfaces only...shift out of 4HI if you are coming upon a dry patch). I even had a '78 F150 that I left the external hubs locked during the winter and would shift into 4HI with a manual shift with no problems. 4LO you must be at a dead stop with the tranny in neutral.

Afterthought: I take my foot off the accelerator before I shift the transfer until the shift is complete. Takes about a second.