Hey guys,

New to the forum and here goes my thread virginity.

So i have a 1995 Blazer that is about to be on its 3rd Transfer Case Control Module this month. The first was fried when i bought it. Replaced it with a used one from a junk yard, which worked perfectly. The other day i was doing a little 4 wheelin and all of a sudden the buttons wouldn't work and it wouldn't go into 4 wheel. Same problem with the first TCCM. So i have another one from the junk yard and going to throw it in but just wondering if you guys had any idea what was causing them to burn up?

PS) I have the cheap posi lock set up that replaces the vacuum actuator with a cable http://diamond.site90.com/html/actuator.html. So i push the button and pull the lever to get into 4 wheel. But right now the buttons don't respond and they only light up when you first turn on the ignition (same thing that happened when the first TCCM went out). Thanks in advanced

 

I suspect your problem is with the used parts.

 

So i guess i was wrong about the TCCM being the problem. I disconnected the battery for ten min. and reconnected it, like others have suggested, and then 4 wheel drive worked.

Now the problem is the 4 wheel hi button stops working. 4 wheel low still works but sometimes it takes a couple tries to get it into and out of 4 wheel lo. The 4 wheel hi button will not respond to being pressed unless the vehicle is in neuteral. When the 4 wheel button does respond (in neutral), it blinks and doesnt do anything, but sometimes 4 hi and 4 lo light up at the same time (but the blazer is only in 2 wheel). Its very sporadic. I was thinking it could be the encoder motor, a wire shorting out, or a solenoid failing. Something is giving the TCCM an error code. Any ideas?

 

You can test the switch with a multimeter set to the ohm scale. Resistances can be found by searching for "NV236+resistance".

 

Well the buttons all work good. So it's not that. Thanks for all the help and the useful threads so far Kyle. You're awesome.

But here is an update. I was checkin the vac lines and the one that goes to the switch on the T-case was cut as in the pic. It should not affect my 4 wheel since i have the pull lever but reconnected it anyways. Not sure if there is a sensor somewhere that reads the vac pressure. I haven't tested the vac pressures on the t case switch or anything.

So i jacked up all 4 wheels and tried the 4 wheel. The back wheels spin and the front driver side spins when in 4 wheel. The front passenger side doesn't always spin. Occasionally it would seem to jolt and start spinning. The front wheels were very violoent when they spin. So i tried spinning the front wheels myself in 2 wheel drive. Both sides spun freely until if felt like it was binding and then it would be really hard to turn. The passenger side, when it got to the hard to turn point, would cause the whole suspension and control arm setup to jump up and down. I am completely confused. My only idea is the part that makes the front axle lock into place on the passenger side of the front differential might be broke. Any ideas??

 

Somehow your posi-lock setup isn't engaging the front axle.

 

Checked the posi lock setup and the "custom part" seems to be working. The cable that goes into the axle will pull up and down. I took the cable housing on the axle off to make sure that moves and it does. The first picture is with the cable pulled and the second is with it pushed in. It only moves about 1/4th of an inch. There is a bit of oil on the cable as you can see in the picture. Not sure if any of this is abnormal. Could the shift fork be bad?



After doing more investigation. I notice when i spin the front driver side wheel (in 2hi) the driveshaft to the front axle spins too. Which explains the resistance on the front driver wheel. Isn't the shaft only supposed to spin when in 4 wheel? Could the transfer case be locked in 4 wheel? I hear the encoder motor click when i push the buttons. Would the vac switch on the transfer case cause this if it was bad? Let me know if this info gives you any ideas what it could be. Thanks

 

The front driveshaft should be free to spin when in 2HI, but if the front axle is disengaged, spinning the driver side wheel should not cause the driveshaft to spin. If there is something creating resistance inside the front differential, causing it to spin, then the front driveshaft will also spin.

If both front wheels are off the ground and the transfer case is in 2HI with the front axle disengaged, you should be able to spin either wheel while holding the driveshaft stationary and the opposite wheel should not spin. If the opposite wheel spins, then your engagement mechanism is stuck in the engaged position.

If both front wheels are off the ground and the transfer case is in 4HI with the front axle engaged, you should be able to spin one wheel and the opposite wheel will spin in the opposite direction. The driveshaft should not turn.

 

Well i have fixed the front axle weirdness. I changed the idler arm and got an alignmet and i don't have any problems with the front axle acting weird. I guess it was a combination of new zr2 torsion bars, bad idler arm, and misc stuff that binded it up. I read that even unevenly worn tires or unequal tire pressure can do that (for anyone that has a problem like that).

But the 4 wheel selector lights are still acting up. It seems that the blazer will do everything right. When you push 4 wheel hi the front driveshaft locks and when you push 2hi it is free to spin. But the lights will either not light up or all of them will light up. Is there an electronic sensor on the transfer case? It seems like the TCCM is getting bad information from a sensor. It will work correctly for a while after you disconnect the battery and reconnect it. I swear i have checked everything. So back to square 1 now that the front axle is working correctly again.

And thanks a bunch kyle that last post was what i needed to solve the axle problem.

 

Fixed the 4 wheel drive. So the problem was the selector buttons. The weird thing was all the voltages checked out according the the factory service manual. I recommend buying a factory service manual. It makes diagnosing your problems a million times easier and more accurate. Withouth the FSM i would have never thought to replace the buttons if all the voltages checked out. I got mine for $50 off amazon.

So i guess i should have listened to Kyle a little better. Well thanks for everything. Oh one more thing. In my attempt to find the problem, everytime i unscrewed the encoder motor eletrical connector it is full of oil. Is this normal?