Strange, my girlfriends 2002 s10 Blazer has that and its right where you said but my 2001 does not have it there and I couldn't find it

 

ok, then on the transfer case, driver side, there should be a vacuum switch with 3 vacuum lines. The switch looks like this:



and you can see its location in this image:



With the engine at idle, unplug the vacuum connector, take note of how it plugs into the switch, there is a locator key so it goes back on correctly. One of the lines should have good strong manifold vacuum. Take note if there is any oil present in the lines.

 

Ill have to check it in the morning and let you know, It might be sunday, we are suppose to get a bunch of snow and my blazer is out front. With checking this what am I looking for?

 

Odd that yours doesn't have the switch on the firewall, 99 and newer have it mounted there.

When the encoder motor performs a mode shift, (2HI to 4HI), linkage inside the transfer case pushes the button on the vacuum switch. The vacuum switch sends vacuum to the front axle actuator under the battery tray. The actuator engages the right outer axle with the right inner axle and depresses an electrical switch on the front axle housing that tells the TCCM if/when the axle is engaged. If it engages, the differential becomes live and you're in 4WD. If it doesn't engage, or the engagement switch doesn't work, the TCCM commands the encoder to revert back to 2WD. That's where you're at We need to figure out why.

 

Whats confusing me the shop tested the thing several times before I got it back and he put it in low,high....and he said the light on the button would blink 3 times and go right in.

 

some shops........... that is all I have to say on this situation.
With what cap is saying. I would guess there is a vac problem ,or a vac switch problem. Since they replaced the tccm and encoder motor.... really, the only thing left is a vac problem.

 

So is there a chance that its is the transfer case?

 

Performing and completeing the mode shift is the end result we're looking for. There is a series of events that must occur before that can happen. At this point, anything is possible. If the transfer case doesn't complete the mode shift, we need to check the things that are involved with commanding and performing it. Could be a bad encoder motor, a bad TCCM, electrical switches, connectors, or wiring, vacuum lines, vacuum actuator, clutch mechanism, (in the right front axle tube) or the case itself. That's why everything needs to be checked. We start with the basic stuff, (common problems with the system) and continue until we find the problem.

If you'd like, I can explain how to manually shift the case. That would tell if the case is the problem. From what you've told us, and what the shop told you, and knowing the reliability of these cases, I doubt that the case is the problem... but, I've been wrong before

 

Well to start I'd like to thank you for your help. Is there a way to but it in 4hi manually?

 

Yup, sure is. Remove the encoder motor and you can shift the transfer case into 2HI, 4HI or 4LO by turning the shaft. Need to take care when reinstalling the encoder though, it must be aligned perfectly or the shift positions will not be correct when using it from the dash switch. The encoder motor is a stepper motor, it moves in increments called "steps" or "counts". Each transfer case shift position has a certain number of counts, like an address on a street. When the TCCM commands the encoder, the counts are monitored by the TCCM so it "knows" the encoders exact position.