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2007 gmc envoy_slt
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6 Posts
Discussion Starter · #1 ·
I have 2007 tb and 4h light would flash and revert to 2h, made checks and found a bad actuator motor. I replaced the actuator and could engage and dis engage the actuator then with scan tool. I can make all the activations and lock transfer case, switch all the indicator lights, and everything seems to work but it wont lock in the front axle automatically. I cleared all service codes from history and I can't get any new codes, yaw and steering all seem to be in the range and work, I swapped out tccm out of my envoy that worked in the envoy, same part #. Anybody have any Ideas, I am new to this forum but I thought maybe some one might have had this experience, right now I would appreciate any help I can get. Thanks
 

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2004 gmc envoy_slt
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2,630 Posts
You may have a bad splined disconnect at the front differential. When you say you changed out the actuator, do you mean the one at the front differential?
 

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2007 gmc envoy_slt
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6 Posts
Discussion Starter · #3 ·
found a problem that should fix it

I am now completely bald. I pulled all my hair out trying to nail this down, as everything seemed to be working, but would not engage by itself. I pulled the encoder motor down and was going to bench test it. I ran all my jumper leads and set up the dvom to watch resistance readings. There was a thread by someone who had posted his readings, so I was going to use those for a reference.(http://forums.trailvoy.com/showthrea...=encoder+motor) This was nice because I can't find them any where else. I couldn't get the motor to turn. I know that it had before in the vehicle. I thought well I am just going to call this one bad and replace it. I put it back in and and then I thought, now I really want to find this problem. I removed the encoder motor again and hooked it all up on the bench and same thing. No data says that when the motor is in lock it will not proceed to next shift or function. The motor will not turn unless it is in lock. Make this story a little shorter I tore the whole motor apart and tested the sensor, tested good according to my experience with potentiometers. I couldn't turn the shaft because of the gear ratio built into it. I removed the metal shell which would be the field and tried to turn the armature and it was rough and would stick each direction after a few turns. I took the whole motor apart laying pieces in order and found on the third layer of gears two gears were broken off with the ears still attached. One gear had a tooth broken, when the planetary gears would turn the main shaft, it would turn so far and then bind up like it had reach the extent of the gear shift. I don't think there is any fix at any reasonable price. Just replace the unit. I was happy just to be able to put my finger on a problem that all made sense for what was going on. A really big thanks to the people who posted their experiences, it really helped.
 

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2007 gmc envoy_slt
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6 Posts
Discussion Starter · #4 ·
to answer envoy boy's question

Sorry, I appreciate your response and yes the front axle actuator. It is rough locking in all the way so I am sure I will need to replace gears or what ever there. I made a slug an put in there so I could manually shift it to make sure that it would. I just want it to try and lock up on command of the tccm and the t case to shift into 4 wheel. and then I'll go on to the next. Thanks again.
 
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