Need a Blazer Guru!

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 working and 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, your axle actuator (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).

quote:

ORIGINAL: rtz28

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 hoses or 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-joint and 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?

Also I did not pull anything vaccume related off of the t-case. Im not sure if what I pulled was the encoder motor or the tccm. I know it sounds bad that I dont kow what it was, but I have or "thought" I had a basic understanding of this system, just not all the terms.

Ok, you pulled off the encoder motor which shifts the transfer case from 2wd to 4hi and 4lo.
If that's working you won't be able to turn the front drive shaft  by hand when you engage 4wd.

The vacuum actuator under the battery just engages the front axles into the front diff and doesn't effect the transfer case
 
 
Just to try to help clarify...The encoder motor (that you removed) is an electrically controlled "motor"
The TCCM (transfer case control module) is located inside the truck and is an electronic module,  looks like a small computer. This is what recieves an input from the switch on the dash and sends a signal to the encoder motor on the transfer case.
 
Before you go any further...have you checked "ALL" your fuses? All fuses under the dash and under the hood.

That is what I orig. thought, so that is what I was going to replace. The one that I got from the junkyard when hooked up but not bolted up I can lay under the truck with it running and have somone hit the button and the little knob inside the encoder motor does not turn. I may have gotten a bad one since it was used, so if I would have seen that knob move that would have been locking in the t-case to 4wd? So it is still poss. that the encoder motor is the problem, or does the tccm control the encoder motor? Thank you for the time, Randy

Yes, the TCCM controls the encoder motor
 

Yes, all fuses have been checked (1st thing I did). I assumed since I was hearing the clicking from the dash on the pass side that the tccm was working, but it sounds like that may be the problem or I got another faulty encoder motor. i appreciate the help very much, thanks Randy

I have to applogize I mistakenly thought you were dealing with the TCCM from some other post I was thinking of, the part that you have is the "Encoder" and it deals with the "range" shifting from 2/4HI to 4LO it will only engage when you are in neutral and coasting under 3mph or stationary.

The front differential locking mechanism is part of the "mode" shifting part of the system, from 2HI to 4HI and back. This part is vacuum operated and can be shifted while moving at according to the repair manual "any forward" speed, I would not go faster than 10mph myself but I don't go offroading to much either (I use it mainly for winter snows).

But when you reinstall the encoder, the bolts should be torqued to 15lb/ft with a torque wrench...

Well, I have a different tccm fron the junk yard I am going to try tonight as soon as I am done here at work. I will post the results when I am done, if anyone has any suggestions let me know thanks Randy

I installed the new tccm and when the button was hit i could see the encoder move (finallly some progress), but I had my wife start the truck and hit the button while i was under it and she turned the truck back off before the encoder was done cycling now its not lined up to be reinstalled. The button now does nothing, no lights or anything. I have pulled the tccm fuse and am going to try to reset it tomarrow after work, and hopefully it will and I can see if my 4wd will finally work. I read that you only have to leave the fuse out for 3 min and then cycle the ignition 5 times for it to reset, I tried that but maybe I didnt leave it out long enough, idk. Any other suggestions let me have em, and wish me luck, thanks alot guys, (chevy lover) (20blazer00) Randy

Turn OFF the ignition.
Remove the 10 amp CTSY LP from the I/P fuse block, and the 20 amp ATC fuse from the underhood fuse block.
Important: Replacing the fuse before the specified time may result in not clearing the DTCs.

Wait a minimum of 60 seconds before replacing the fuse. Once the fuse is replaced DTC 1 will be set in the transfer case shift control module.
Cycle the ignition switch from the OFF position to the RUN and back OFF five times in order to clear DTC 1 from the transfer case shift control module memory.

Glad to hear of your progress.....oh, you were so close. I don't know if you can turn the slot in the encoder motor to align it with the shaft. If you can, I'd install the encoder motor and then test the system.

Well, I went back to the junk yard got another encoder motor and came home and installed it and, guess who has 4wd now <----- this guy. It turns out the first encoder I got was junk, it worked the one time, I guess on a fluke. Thank you guys, chevylover, 20blazer00, for all the help getting this fixed, very much appreciated thanks, Randy
 

I'm always happy when I hear that a problem has been resolved. Good job rtz28.