KyleStubbins.com

Hi John;

I can only comment on / give advise for problems that I myself have encountered as I am not a mechanic. Unfortunately, yours is one I have never encountered and would suggest taking it to a mechanic.

Regards;
Kyle

I have a similar problem that popped up on our Blazer a week ago. Dropped into 4whl on it's own. I was able to get it to shift out and finally got it to shift into 2whl hi. I tried resetting it by disconnecting the battery and it would reset and come back in various positions including 4whl low and 4 whl high. But now the only thing I can get it into is "auto 4 whl" and the 4 low light will blink occaisionally. Looked into the TCCU for corrosion and found none, so figuring a bad TCCU located and installed a new one. NO change, vehicle still stuck in Auto 4 whl. Have ordered a new dash transfer switch, but am not confident that will cure problem.

Still awaiting the arrival of new dash switch, but thought I would attempt to do a little diagnostics on the electrical to the TCCM. I have read thru all the previous posts on the forums and even downloaded the wiring schematics I found there. Surprise! The wiring on my TCCM connector on my 2001 is not at all the same as on the schematics posted previously. For example, I have NO orange wires going into my connector. Of course that makes it impossible to trouble-shoot using that schematic.

Jim

I too could not get out of 4Lo until it finally went into auto 4wd. Now it is stuck in auto 4wd and I cannot get into 2wd. Briefly I had 2wd but it quickly dropped back into 4Lo. Both 4Hi & 4Lo have not responded at the dash switch for about a year so I was suprised to have it drop into 4Lo by itself. I had corrosion on my 32-pin and 4-pin connectors on the TCCM which I have cleaned and reassembled per your advice, thank you. Looking forward to your reply and thanks very much Kyle!

Kyle's reply;

Hi Wayne;

The only time I had a problem with the actual shifting into 4WD the problem was caused by a set of "forks" within my transfer case that were worn and not allowing the gears to fully seat into their proper positions. Unfortunately, that's all I can really tell you as I'm not a mechanic and did not do the work (I took it to a transmission shop which resolved my issue).

Regards;
Kyle

Well, this is good news. Received my replacement dash transfer control switch today and that was indeed the problem. As soon as I switched out the old switch the system returned to operation. One thing I can note about this in addition to the symptoms I already indicated is that when I turned the ignition on after replacing the switch I note that the new switch lights up about three times as brilliant as the old one. I did not notice just how dim the lights had become on the old switch, so if your switch is somewhat dim good chance that is the problem with your system and not the TCCM.

Jim

Kyle's reply;

Hi Jim;

Wow! That is good news! Sometimes it's the things staring right at you, eh? :)

Thanks for posting your efforts and results... I'm sure it will help someone out with the same problem!

Regards;
Kyle

I lost my nerve and took mine to a shop. The mechanic working on it tried replacing the dash switch but it did the same thing. Once I know for sure what the culprit is
I'll post for future reference. Glad to hear your problem was relatively easily solved.

Kyle's reply;

Hi John;

Yes, please do post back with your results as I'm sure it will help someone out in the future. I can only give advise on what I have personally encountered with my own Blazer -- unfortunately, I have not had this problem, so your advise would be great!

Thanks!

Kyle

Hello, First of all I want to say "Thank You" for this wonderful blog. I have gained allot of information from it. I have a question regarding my wifes '99 Blazer. She bought it used with it stuck in 4hi. The previous owner used to pull the fuse from the fuse panel on the drivers side of the dash to disengage the 4wheel. he had replaced the push button on the dash, but that did not take care of the problem. He said that we would need to replace the TCCM. We have not replaced it due to financial reasons. Three days ago my wife left work to come home. For some reason it was locked in 4low. She removed the fuse, but no change. So she had to creep it home at 20 MPH.I will be checking it out this evening. According to a few posts in your blog, I should be able to manually disengage the 4low by removing the encoder motor and moving the actuator. Can I then put back the encoder motor and drive it until I have the finances ($500!) to replace the TCCM, or would it simply re-engage the 4low. One other option would be to put 12 VDC directly to the encoder motor to disengage the 4low and then leave the wiring disconnected to prevent it from reengaging it. I understand you are not a mechanic, but any help you can give is greatly appreciated.

Hi David;

Hi David;

You can move the actuator to disengage 4WD, but you may have to leave it disconnected as it might not line up when you try to put it back on (the actuator may not line up with the encoded motor after the actuator has been moved -- but you may be able to move the encoder motor to match, I don't really know as I've never had to do this).

I wouldn't go the 12V route to the encoder for a couple of reasons;

1) the motor itself is 12VDC, but the "signal" lines are 5V. The signal lines are the lines that tell the encoder which mode to put it in -- check the schematics here --> http://kylestubbins.com/files/TC_encoder_motor.jpg.

2) you'd have to cut/strip wires to the encoder, which makes for more repairs and possible problems in the future.

3) you risk damaging the encoder motor.

I would look at the TCCM, if you haven't already. There may be corrosion on some of the wires that could be fixed. Then, I'd look at the wiring to the encoder motor, just to make sure that's good too. It's worth a shot!

Good luck and let me know how you make out (or if you have any other questions I may be able to help with).

Regards;
Kyle

Hello Kyle I have a 94 s-10 blazer and when i press the 4hi switch when the car is in drive nothing happens. but if in nuetrul I can hear the edcoder moter working but the ligts dont always stay on. I repalced the tccm with one that i go at a walk thru scrap yard for 20.00 and it worked for about a day then stoped again. i also replaced the vac switch on the tc as it was deffently bad
an again it work for about an hour or so then back to only nuetral. any sugestions.

thanks

Kyle's reply

As I am not a mechanic, everything that I know about the Chevy 4WD system has been posted here. If you haven't found the answer in what I have already posted, I don't have the answer you're looking for.

Regards;
Kyle