Im somewhat new to the forums and have seen the all the 4x4 help that was offered, so I have a question. I have a 92 blazer 4.3 electric t-case. My 4wd is not workingand I think I have it narrowed down to the actuator on the t-case. my question is with the actuator off the t-case but still pluged in should you be able to see the little blck plastic (spline-gear) move when you hit the 4x4 button? My t-case is not locking in, when you hit the button it just blinks for 15-20 seconds and goes back out, and even when its blinking you can still turn the driveshaft by hand. So I picked up a actuator from the junk yard and same thing, did I just get a bad one or does the prob lie somewhere else? Thanks alot, Randy

P.S. - There are no 4x4 dtc codes either

 

Hey there, I just fixed my 4 wheel drive and for me it was just a disconnected vac line...make sure that you check the vac lines coming out of the back of the intake, there is a hose that connects to a T nozzle that goes to your different accessories, i.e. window washer reservoir,youraxleactuator (underneath the battery tray in the front of your engine compartment), and also to you HVAC controls and then to your Vacuum canister. Check them all out and if they are loose, dry rotted etc, replace them. it is an easy and cheap fix for the 4 wheel drive. Now, if your T-case isn't locking in, then even if the hubs are working it won't go into 4 wheel. I haven't dealt with the transfercase part of it, so Im afraid I offer no help in that situation.

 

I have made sure all vaccume conections are good, and like you said the t-case is not locking in so I think that the actuator is the problem, just trying to see if I got another bad part or if ther is something else going on. I appreciate the help and response alot, thanks Randy

If anyone else has any suggestions while the driveshaft and yolk is out it would be appreciated, I would like to save myself from having to do this again (pita).

 

The acuator that you removed from the T-Case is for 4HI -4LO if you are having trouble locking in from 2HI - 4HI then there is a vacuum switch(acuator) at the top of the T-Case drivers side with 3 lines, it controls the vacuum for the 2HI - 4HI vacuum actuator under the battery box.

There is a cable from the front axle that goes under the battery. Sometimes this cable becomes inoperable from lack of lubrication...and sometimes the actuator it is connected to gets a leak in the diaphram which makes it hard to get into 4HI...

These should get you close to the problem if not finding it...

 

That makes sense, because that little spline only moves into two positions, i will get to that actuator on top of the t-case then, do you know if I am supposed to see that spline move when its hooked up and the button is hit, or does the vaccume interfere with that? Thank you very much, very very much appreciated, Randy

So if the t-case is not locking in should I be looking at the actuator on the t-case with the three hosesor the one under the battery box?

 

The actuator that you pulled of is called the Transfer Case Control Module (TCCM) it only controls 4HI to 4LO when you engage the button it should move...if not then the TCCM is either faulty or the connector is bad. You would need a DVM to check voltages.

But for 2HI to 4HI you would have to check the actuator under the battery tray or the vauum switch on the T-case they did update the design so that it was more durable, there was a problem with it sucking up T-case fluid all the way into the HVAC controls in the dash...

 

There are 2 parts to your 4X4 action. Electrical and vacuum.
Electrical = dash switch
TCCM (control module) located in the right front kick panel or in the dash behind the glove box
Encoder motor mounted on the left rear of the transfer case
These components work to lock the transfer case into 4wd, which locks in the front drive shaft to turn the front differential

Vacuum = intake vacuum to vacum resevoir (round ball on the l/rear of the engine area
vacuum diapraghm under the battery tray ( pulls a cable at the right front axle)
vacuum switch on the right side near the top of the transfer case
The vacuum works to lock the front axles into the front differential when the transfer case is locked in 4wd.

From your original post it sounds like you have removed the encoder motor.

Can you tell me how you "narrowed the problem to the actuator on the transfer case", and does what I have written make sense to you?

 

It makes perfect sense. I "thought" that the actuator I pulled off was what locked in the t-case, (from other post Ive read). That is my problem it is not locking in, when I hit the botton it just flashes for about 20 seconds or so and I can hear a clicking from the dash but then the light just goes back out and nothing happens, while doing this I can still turn the driveshaft by hand so I know the t-case is no locking in. I thought this was the mech. part so i ruled out vaccume as a problem. Obviously I went about this the wrong way, and do not know as much about the system as I thought I did, so where do you suggest I start now?From what it sounds like the vaccume actuator under the battery box just controls the cable to lock in the front diff and wouldnt really have anything to do with the t-case engaging is that correct? Thank you again, Randy

 

Actually it sounds like you were on the right track. If it's not the encoder motor, it's probably the TCCM located under the dash by the glove box or behind the right kick panel.
I'll see if I can find some diagnostics, but you already have tried the encoder motor on the transfer case, the lights work on the switch, so that basically leaves the TCCM and the wiring.

 

The part that I pulled of was bolted two the t-case with three bolts, located between the u-jointand t-case, and had an 8mm bolt connecting the harness to the unit, that part only controls 4hi to 4lo? If so would that have any impact on the t-case engaging? Also it sounds like the vaccume actuator under the battery tray only controls the front diff and have no bearing on the t-case, is that correct?