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Discussion Starter · #21 ·
update without new parts

Saturday I got up and decided to change out the wheel hub bearing and half shaft on the driver’s side. All went well and I changed the front diff lube while I was there, it looked a little too metallic for my taste so I will change it again soon. I changed the TC lube and that drained out like it was new. Sunday the Envoy was still in the shed so I started to work on the passenger side, when I got the shaft out of the disconnect case I couldn’t resist unbolting it even without the parts I ordered weeks ago. When I took it apart, it looked Ok, but it wasn’t engaging? After a good cleaning, the wheel side gear and bearing showed signs of failure also the grease in areas was similar to hard plastic. The large diameter on the fork where it rides in the case and the bore it rides in was scuffed up. Fine sand was inside the O-ring area where the electric actuator attaches. Without new parts and I need the vehicle, all I could do is deburr/polish and assemble. Before I put the tire back on I had to check to see if it shifts to engage, the actuator seemed to run a few seconds longer than before, I turned the hub and I could feel the gears engage. Got it all together and was going uphill to the front yard in 2wd and the rear tires spun so I put it in 4wd, it pulled up the hill and when I turned to the driveway I got that 4wd hop. When the parts come in I need to change out the bearings and I will swap out the fork, inner/outer gears and shift sleeve with the awd connecter sleeve. After looking at this assembly close up I see another advantage to the awd sleeve, it is supported over a span by 2 bearings where the outer gear is only supported by 1 bearing. It makes sense that lifted frontends will add more stress in this area. BTW, on a scale of 1 to 10 this is a 7 cigar job. bstromback2002, thanks for checking to see if the front shaft is turning. Your findings prove my theory that when you get going it’s all turning. Your right about the parts I want to swap out, check out my first post of this thread. Thanks all for your input. :hail:
 

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I don't mean to nag, but I just stumbled across this thread and was wondering if you had received the parts and had a chance to put it all together? I need to fix my disconnect, too, and with all the other things that should be fixed, would like to spend as little money as possible on it, as long as it works well.
 

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Discussion Starter · #23 · (Edited)
No nag, I am waiting for the parts and they are waiting for seals to ship complete. I will say, it was worth my time to take the disconnect apart, clean it up and repack with new synthetic grease. It works well now and I have bought some time until the parts come in. I was worried that it was getting worst by driving it, I did not want a complete failure of this unit. If you have 4 hours to ease your mind it is worth it. We expect snow tomorrow and I am glad to have it working. Best of luck.
 

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Thanks for the update. I'm excited to see how it turns out, even though I think I just found an easier way out for myself.

I had contacted Nordstroms Auto (mentioned in other disconnect threads) a while back about getting one of these with low miles, but they didn't have anything at the time that I would want to put in without rebuilding first. They called me this morning saying that they had just received a 2006 with 60 miles on it and would sell me the disconnect w/actuator for $200. I should have it tomorrow. I think I'm going to pull it apart and re-grease everything before I put it in, but it will make my life a lot easier to be able to just unbolt the old one and bolt the new one in.
 

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Discussion Starter · #25 ·
That sounds like a good deal and to have some spare parts to boot. A word of caution, be carful and gentle when removing the disconnect case from the oil pan. Aluminum to aluminum will oxidize and be tough to remove, take the skid plate off to get a good view of the assembly connection and gently pry and wrap the case with your hand to get it to loosen. Some of the posts here have mentioned broken cases and oil pans when separating the two. Be sure to get all the bolts and best of luck.
 

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Discussion Starter · #26 · (Edited)
Update

Update; I got the stuff, well almost all of it. I ordered the parts 4 weeks ago and CompNine is a real company and they do ship, just a little slow, however the outboard seal is on back order so I will see my local dealer and hope they can get one for me soon. The clean & re-grease I did a few weeks ago is still working fine, :thumbsup: the bad weather keeps me checking to see if the 4x4 is working. I am still excited about making this change and will keep you posted.
 

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Discussion Starter · #27 ·
The deal is done; I by-passed the disconnect fork. Sorry it has taken so long but the priority list is extensive, however this task came to the top of the list. As mentioned at the start of this post, using the original disconnect case I changed out the fork, engagement sleeve, inner & outer gear for a AWD sleeve and while I was in there I changed all bearings and seals. When you put it in 4wd you can hear the TC shift and the front electric actuator activate and quickly, all it is doing is pushing air. All the controls are working correctly and no 4x4 service light. The 4x4 is working per a quick little acceleration in the yard, took a ride up town, down the power lines and on the highway for a bit, it all seems fine. I will update after I run a few tanks of fuel through it. For you guys that failure is not an option this may be the mod for you. Parts about $200, time for mod about 4 hours, being in 4wd, priceless. This is one happy camper that is ready for the beach. :woot:
 

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Good to hear! At least we now know we have this option.
 

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Discussion Starter · #29 ·
It has been a few weeks and 4 tanks of fuel since I modified the front axle disconnect assembly with bypassing the disconnect system so I will give you a follow up on how it has been so far. My mileage, mostly highway driving was reduced 1 mpg, even though I have a set driving routine and am a creature of habit, one notable variable has been warmer weather and the AC is running more often, thus 1 mpg lower maybe no real change? I have not noticed any acceleration or just plain driving differences, no vibration or noises so the modification worked the way I expected. One less thing to worry about. :woot:
 

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Hello,
I want to bypass the fork of the disconnect. I think I will simply buy a new disconnect asssembly designed to the SS. The electrical actuator is still needed in order to send the logical signal to the TCCM. Since I don't want to use the electrical actuator, I decided to build a small circuit that will emulate the actuator. As I understood, when the 4x4 switch is moved to the AWD or 4H position, the actuator receives a trigger signal (HIGH) from the TCCM to its "A" pin (light blue wire). Then, the actuator sends an output signal from its pin "C" to the TCCM through the black/white wire. This output signal is LOW when the shaft is extended (4x4) or HIGH when the shaft is retracted (2x4). I got this information from the couple of posts on this forum. So, basically instead of using the actuator,one can build a small circuit that will send LOW signal to the TCCM by the black/white wire when the HIGH signal is received by the light blue wire. There are plenty of possibilites here: 1) a simple NPN transistor in a common emitter configuration, working as a logical inverter circuit; 2) a combination of (1) and a timer circuit based on LM555 (to produce a time delay between the input and output signals); 3) a microcontroller (ATTINY85, for example) that will receive an input and produce an output with a time delay between them. To build this circuit, I want to know the voltage levels of the TCCM signals. Of course, I can measure them but maybe somebody can provide me with this information? Are the TCCM signals regular 0-5V? Also, do you think that the time delay between the input and output signals is necessary?
Thanks!
 

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I'm not so sure there is a logic module down there. Thinking it is just a microswitch perhaps. Anyway, the signal back to the TCCM on a blk/wht wire to pin B6 of Connector 2 of the TCCM is battery voltage when front axles locked and essentially zero (maybe 20 mV) when front axles unlocked.
 

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I'm not so sure there is a logic module down there. Thinking it is just a microswitch perhaps. Anyway, the signal back to the TCCM on a blk/wht wire to pin B6 of Connector 2 of the TCCM is battery voltage when front axles locked and essentially zero (maybe 20 mV) when front axles unlocked.
Yes, there is a kind of a switch inside the actuator - a several stripes on the PCB and a metal contacts that move together with the actuator's shaft and make a contact to the stripes on the PCB . Maybe a simple relay could be used to emulate this switch of the actuator. However, the delay between the trigger and output signals could be needed since it takes a few seconds for the actuator to move. It seems that the signal on blk/wht wire is either 12V or about 0V.
The main question is what is the HIGH voltage of the control signal from the TCCM (lt blu wire on pin C1/A2 of the TCCM)?
 

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The main question is what is the HIGH voltage of the control signal from the TCCM (lt blu wire on pin C1/A2 of the TCCM)?
Just backprobed that one at the TCCM like I did the blk/wht. A little less accessible than the blk/wht but not real difficult. Same voltages seen but in reverse order. Battery voltage unlocked, up to 90mV locked.
 

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Not sure if this has any bearing on your plans but I tested something else and determined the battery voltage on the blk/wht appears to be sourced from the 4WD fuse in the rear fuseblock. I concluded this by removing the 4WD fuse while in A4WD. The backprobed voltage on the blk/wht went away and the mode switch changed from solid A4WD to A4WD flashing and a solid light at 2Hi. Without the 12 volt on the blk/wht I guess the TCCM reverted to a state of attempting a shift from 2Hi to A4WD??

Also, when the TCCM determines a successful shift has been made a message is sent in the class 2 data bus to the functional address 3B and is acknowledged by the PCM and the EBCM. I won't claim to have even the slightest idea of the purpose of this messaging.
 

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Not sure if this has any bearing on your plans but I tested something else and determined the battery voltage on the blk/wht appears to be sourced from the 4WD fuse in the rear fuseblock. I concluded this by removing the 4WD fuse while in A4WD. The backprobed voltage on the blk/wht went away and the mode switch changed from solid A4WD to A4WD flashing and a solid light at 2Hi. Without the 12 volt on the blk/wht I guess the TCCM reverted to a state of attempting a shift from 2Hi to A4WD??

Also, when the TCCM determines a successful shift has been made a message is sent in the class 2 data bus to the functional address 3B and is acknowledged by the PCM and the EBCM. I won't claim to have even the slightest idea of the purpose of this messaging.
The feedback signal (blk/wht wire) gets 12V from the brown wire through the switch (basically, the stripes on the PCB and a metal "fingers") of the actuator (encircled in red in the attached schematics). The brown wire is sourced from the 4WD fuse, that's right. When the fuse is removed, there will be no movement of the motor and no 12V on blk/wht wire. There will be no attempt to shift from 2Hi to AWD, probably because the feedback pin of the TCCM is neither high or low, it is now floating. More correctly, that pin is probably normally pulled up and cannot be really floating, so when there is no power to the actuator, the feedback signal cannot be low and the TCCM recognizes it as high.

The communication of TCCM with the PCM and the EBCM is not that impotrant for the emulation of the actuator, I think. I will build a circuit that will take the control signal and send the (inverted) feedback signal back to the TCCM, exactly as the actuator. I think I will introduce a delay of 1-2 seconds between the control and the feedback signals just because it takes some time for the actuator's shaft to move and activate the switch inside.
 

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I have wiring diagrams but they only show the actuator as a simple block with no internals detailed.

What I was observing was that from the perspective of a driver, if the 4wd fuse were to fail, the mode switch will display identical conditions (lighting) to an attempted shift in progress from 2Hi to A4WD.

Incorporating a delay seems logical. Do you know if the TCCM calibration differs in the AWD models of the TCCM?
 

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OK, an update - I created a circuit that receives the 12V signal and inverts it after a delay. However, I am somewhat confused. In the first post here it is written that "the control signal from the TCCM goes high to command the actuator to extend its probe for 4WD, and goes low to command retraction for 2WD. There is a feedback signal that confirms to the TCCM that the actuator is working, and it sends a low for extended and a high for retracted". My circuit is working similarly. However, I just realized that Mr. TJBaker described the reverse situation: the control signal is "battery voltage unlocked, up to 90mV locked " and "the signal back to the TCCM ... is battery voltage when front axles locked and essentially zero (maybe 20 mV) when front axles unlocked". Which situation is correct?
 

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OK, an update - I created a circuit that receives the 12V signal and inverts it after a delay. However, I am somewhat confused. In the first post here it is written that "the control signal from the TCCM goes high to command the actuator to extend its probe for 4WD, and goes low to command retraction for 2WD. There is a feedback signal that confirms to the TCCM that the actuator is working, and it sends a low for extended and a high for retracted". My circuit is working similarly. However, I just realized that Mr. TJBaker described the reverse situation: the control signal is "battery voltage unlocked, up to 90mV locked " and "the signal back to the TCCM ... is battery voltage when front axles locked and essentially zero (maybe 20 mV) when front axles unlocked". Which situation is correct?
Indeed I noted the same discrepancy and that was one reason why I worded my post using 'battery voltage' to be clear of my observations.

I will double check this evening but I am fairly certain my post on the state of voltages is what I observed.
 
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