TC Motor

ts684

Member
What position should the TC motor shaft be in when in 2WD? Motor came with a plastic "key" holding it in position but I had to turn the shaft on the TC in order to install the motor. The "half moon" cutout on the motor was generally pointing to where the wiring entered. If I did not turn the TC shaft I could not install the motor. I believe I turned it a bit clockwise.
 

MRRSM

Lifetime VIP Supporter
Try viewing this article and in particular...look at the attached diagram for the Two Wheel Drive Flow Path imagery:

All information via TV Links and Images:


2wd-flow.jpg
 
OP
OP
T

ts684

Member
Uhh, OK, but that does not answer what I need. I viewed a u-tube that showed how to turn the TC shaft counterclockwise to be sure it is in 2wd. I did that, but then could not mount the new TC motor without moving the TC shaft back to the original? position. I won't be able to check further until maybe Wed when I have some time.
If I remove the new TC motor, keeping it connected, if I turn ignition on and turn selector switch to A4WD then 4WD, then back to 2WD should the shaft turn and return to correct position?
 

MRRSM

Lifetime VIP Supporter
It might...but this is a "Which Came First... The Chicken or The Egg?" sort of Problem in that, prior to removing the Old TC Motor... My guess is that 'the innards' of the Transfer case may have components that also needed to be Pre-Set in the 2WD Condition to match the set up of the New TC Motor in the 2WD Setting.

You might give the local AAMCO Dealership a call and see if you can coax an answer from one of their Service Techs as to whether or not this can be achieved AFTER the Drive Motor has been removed. Without having the exact original conditions at play known ahead of time... you might have to resort to setting the Drive Motor in whatever the Selector Position on the Switch in the Cab was sitting on just before you began your disassembly.
 
Last edited:

HARDTRAILZ

Moderator
It might...but this is a "Which Came First... The Chicken or The Egg?" sort of Problem in that, prior to removing the Old TC... My guess is that 'the innards' of the Transfer case may have components that also needed to be Pre-Set in the 2WD Condition to match the set up of the New TC Motor in the 2WD Setting.
WTF? No old TC was removed?

You might give the local AAMCO Dealership a call and see if you can coax an answer from one of their Service Techs as to whether or not this can be achieved AFTER the Drive Motor has been removed. Without having the exact original conditions at play known ahead of time... you might have to resort to setting the Drive Motor in whatever the Selector Position on the Switch in the Cab was sitting on just before you began your disassembly.
Wow...


@ts684 I have a spare motor in my garage. I removed it while in 2wd so it should be clocked where I can answer your question with first hand knowledge. I do think the half moon n wiring were generally lined up though. Can double check when i get home, but may be late.

However by now have you tried to see if is working? Also, what do you consider turning it "a bit'?
 

Maverick6587

Silver Supporter
Even though he turned the TC shaft. As long as @ts684 can connect the TCCM to the TC shouldn't the TCCM re-calibrate/learn once the vehicle is turned on? i.e match/change to the 2wd or 4wd that the TC is currently in?
 

TJBaker57

Well-Known Member
Maybe this will help.....

1st image = 2004 Envoy in 2Hi

IMG_20191207_123146.jpg

2nd image = 2002 TrailBlazer in 2Hi

IMG_20190701_125024.jpg

3rd image = Internal view of an original equipment range position sensor. Note the 4 fixed locations indicated by the flags and the 1 range which I believe to be the A4WD range. The fixed positions denoted by flags suggests to me the modes are a fixed location, not learned through some calibration routine. In a number of sources I have read of specific voltages expected at various mode selections, again suggesting these are fixed locations.

IMG_20190702_172704.jpg
 

budwich

Well-Known Member
IIrc, the motor has no "natural stops". IF you power it with out it being connected to the case, it will ultimately spin 360 degrees. The problem with that is that the "wiper fingers" may cross over areas that could cause a problem with the contacts, causing them to jam or otherwise damage things. Look at the posted picture of how the contact fingers are sitting.... not good if they cross over a discontinuity in the plane.

The tc shaft has a "fixed range" such that it can only travel in a "sweep" / turn of so many degree (I think the preposted diagram shows that range to be about 70-80 degrees). This is what keeps the overall system "sane". I do believe that the plastic key on the motor is to hold the motor in a "valid position" during "shipping" so that the motor can be readily placed on the tc shaft which can be in any position that allows that to happen. IF correct, the controller will do its measurements to determine where that is based on the electrical "readings".

Having said that, one should be able to put the tc shaft in the known 2w position (someone indicated where that is ... ie all the way clockwise or counterclockwise). Once there, a battery supply can be used to "bench energize" the motor and move the offset to the right position... keeping in mind the comments about not turning the motor too far in any one direction. Closely examine the harness position along with the bolt layout to align things accordingly.... the last picture just posted should help.
 
Last edited:
OP
OP
T

ts684

Member
IIrc, the motor has no "natural stops". IF you power it with out it being connected to the case, it will ultimately spin 360 degrees. The problem with that is that the "wiper fingers" may cross over areas that could cause a problem with the contacts, causing them to jam or otherwise damage things. Look at the posted picture of how the contact fingers are sitting.... not good if they cross over a discontinuity in the plane.

The tc shaft has a "fixed range" such that it can only travel in a "sweep" / turn of so many degree (I think the preposted diagram shows that range to be about 70-80 degrees). This is what keeps the overall system "sane". I do believe that the plastic key on the motor is to hold the motor in a "valid position" during "shipping" so that the motor can be readily placed on the tc shaft which can be in any position that allows that to happen. IF correct, the controller will do its measurements to determine where that is based on the electrical "readings".

Having said that, one should be able to put the tc shaft in the known 2w position (someone indicated where that is ... ie all the way clockwise or counterclockwise). Once there, a battery supply can be used to "bench energize" the motor and move the offset to the right position... keeping in mind the comments about not turning the motor too far in any one direction. Closely examine the harness position along with the bolt layout to align things accordingly.... the last picture just posted should help.

Ok. The TC motor as delivered had the shaft in the same position as in the picture. I think I read and also saw a U-tube vid showing the shaft on the TC being turned counter clockwise to get into 2WD. When the shaft is in this position, the motor can't be installed because it hits the TC case. I turned the shaft a bit clockwise, like from 11 to 12 o'clock, so I could install the motor. With all four wheels in the air , got a lot of blinking lights, A4WD went to a steady light on 4Hi, got front wheels spinning, did manage to get it back into 2WD but ran out of time to test further. In the picture of the transfer case, does the half moon point up or more forward? Like 12 vs 11 o'clock.
Also with the motor not installed but the wiring connected, will turning the ignition on and moving the selector switch from 2WD to A4WD to 4WD and then back to 2WD put the motor in the correct position?
 

budwich

Well-Known Member
I can't remember / answer that as I used the "bench method" to position the motor to a position that allowed the install.... and after that things were fine.

From your post, I am not sure what you are indicating... currently do you have a problem? It sounds like things are functional with lights on the selector functioning correctly and the system engaging accordingly.... maybe I am not reading the post correctly.
 
OP
OP
T

ts684

Member
With all wheels off the ground, with car running, I moved selector switch to A4WD. After a lot of blinking, the light on 4Hi lit steady even though the switch was not set there. Turning switch back, I got blinking on 2WD. Turned car off, disconnected battery, waited a while, reconnected, back in 2WD. Ran out of time for further checking.

You mentioned "bench method", could you give me a link?
 

Maverick6587

Silver Supporter
What budwich is asking is, have you installed the new motor onto the transfer case?
From what you have been stating, with switching from A4WD to 2WD... it sounds like you have installed the new motor and it is functional now?

The "bench method" budwich mentioned, is to position the motor's gear so that it could be installed onto the TC.
 
OP
OP
T

ts684

Member
The TC motor as delivered had the half moon notch In the same position as in the photo. Even though the TC was supposedly in 2WD with the old TC motor, I had to turn the TC shaft 1 notch clockwise in order to mount the new motor. After reconnecting the battery and starting car, I moved selector switch to A4WD. After much blinking, the light at 4WD lit steady even though the switch was not pointed at 4WD. Not what I expected. Car in gear but off the ground, front wheels seemed to be turning at half speed of rear. Turned switch back to 2WD, blinking at 4WD, then blinking at A4WD, then steady at 2WD. I didn't go further since I was out of time. Don't get video, it's not for TB/Envoy.
 
OP
OP
T

ts684

Member
Since it is a different type of mechanism on a different vehicle, I would say it doesn't apply.
In the 4th photo from TJBaker57, I would like to know where the half moon points.
 

TJBaker57

Well-Known Member
In the 4th photo from TJBaker57, I would like to know where the half moon points.
The 4th image is unfortunately the sole image I have that shows the TC Range Selection Shaft. And as you have noted it isn't exceptionally clear when it comes to indicating the shaft rotational position.

However,,, the second image is the actual shift motor removed from this same transfer case at the same time so we can use that image to further define the shaft position as the half moon is clearly in view straight on, albeit a mirror image.

Looking closely at the sensor wiring terminals we can see they are labelled "A, B, & C". Let's call the B terminal, which is also the center of the wiring connector, the zero position. It looks to me that half moon is rotated about 10 or 12 degrees clockwise from the B terminal. In that this exact shift motor was just removed from the corresponding transfer case shown in the 4th image then we can say the transfer case shift shaft is rotated about 10 or 12 degrees counter-clockwise from the center of the wiring connector & the B terminal.

Does this help?
 

TJBaker57

Well-Known Member
After reconnecting the battery and starting car, I moved selector switch to A4WD. After much blinking, the light at 4WD lit steady even though the switch was not pointed at 4WD

Have you considered the selector switch as a possible trouble source? I know early models were known to be an issue but I don't know about late models. The selector switch returns a voltage to the TCCM to indicate what mode is selected. The TCCM would then flash the light(s) while attempting to make the shift. The light(s) would turn steady once the shift was successful. The contacts inside the switch were known to become dirty and then not return a correct or steady voltage to the TCCM. Unpredictable operation can then result. A tech 2 scantool can monitor this return voltage signal. I had issues with my 02 and ordered a replacement mode selector switch but before it arrived I took the original switch apart and cleaned the switch contact surfaces and haven't had a problem since. I keep the new replacement as a spare.

IMG_20190321_150817.jpg
 

budwich

Well-Known Member
The TC motor as delivered had the half moon notch In the same position as in the photo. Even though the TC was supposedly in 2WD with the old TC motor, I had to turn the TC shaft 1 notch clockwise in order to mount the new motor. After reconnecting the battery and starting car, I moved selector switch to A4WD. After much blinking, the light at 4WD lit steady even though the switch was not pointed at 4WD. Not what I expected. Car in gear but off the ground, front wheels seemed to be turning at half speed of rear. Turned switch back to 2WD, blinking at 4WD, then blinking at A4WD, then steady at 2WD. I didn't go further since I was out of time. Don't get video, it's not for TB/Envoy.
I am still not sure what you are saying. Currently, is your vehicle in 2W mode with a solid light indicating such? Further, if you select other modes, what is the result NOW? ie. do some "complete" testing. I would suspect that your system is operationally OK.

Further... what was the original problem as to why you replaced the motor?
 
OP
OP
T

ts684

Member
Original problem was not being able to get out of 4WD. TC motor sounded like it was "cycling" then nothing. Turning car off overnight, back to 2WD next day.
Since no sound from TC motor, I replaced. No sound from front disconnect, I replaced.

This is what I have now. With all wheels off the ground, trans in neutral, ignition on.
Turning switch to A4WD produces a sound somewhere, can't say for sure if it's the TC motor (bad hearing). Front wheels can be turned independently! Lite over 2WD is steady, lite over A4WD is flashing and does not go to steady. Turning to 4WD, another sound, think it's from disconnect. Now, front wheels cannot be turned independently. Lite over 4WD is flashing and does not go steady. Lite over 2wd is steady. Turning switch to 2WD, 2 sounds, and back to 2wd. Sometime during this testing, the service 4WD lite came on, disconnecting battery cleared. I would be OK with 2WD and 4WD and no A4WD. Any idea why lites keep flashing?

TC motor as delivered had shaft in position pictured. Turned TC shaft 1 "click" counterclockwise, could not install motor, turned shaft back, installed motor. Since TC should have been in 2WD at the time, not sure why I could turn shaft.
 

budwich

Well-Known Member
OK.... that's gives a more clearer picture of where you are and where you have been..... definitely in the "swamp" now and the "alligators" are wondering around...:smile:

I am not sure at this point that I can provide much more help as I have only limited experience with my 2008 (replaced the tc motor) and don't have access to the service manual system that I followed at the current time or near future.... :-(

Having said that, I will still try and at least state a few things that I hope will help.... maybe.... and maybe it is some of my misunderstanding of operation... so please take things accordingly.

First, I don't believe in "A4WD" (which I think in 2008 is "AUTO"), that the front disconnect operates at the time of the switch movement. Its operation is based on speed sensors and TCCM controls deciding when to cause "front wheel" efforts. However, the issue of seeing lights flashing on the switch should not happen. They should go solid to the selected operation.

It would appear that selecting 4WD causes the system "almost" respond correctly physically but results in "flashing lights" :-(

It would be nice if you had a way to get at the system with a scanner (equivalent of the tech2 or otherwise) that can read the TCCM. That would quickly tell you what's up. The problem now is you are currently thinking that the method of replacing the motor is your source of the issue (the service manual would confirm this) BUT it may not be true as the wiring / connections might be the issue also. There was a post a bit ago where someone had some wiring issues which the tccm codes pointed to.

Based on your latest description, it sounds like the switch is fine as the system is commanding properly.

One more test that you can try is attempting to go from 2W to 4WD without being in neutral. You should not hear anything as this operation is not "allowed". The lights should do something (can't remember what... probably dance from the selection back to the 2W). Probably doesn't help much other than another data point.

At this point, I am sorry that I can't narrow things down more or provide much better guidance.

I guess there are a few other tests (in similar fashion) that may be able to check things out further but require more work (ie. removing the motor). For instance, You indicate that can somewhat put the system in 4wd. Do this (confirm with your ear or otherwise), take the motor off and observe where things are on the transfer case shaft position. I would expect that the position should be in some "known position" (ie. furthest stop). That may indicate that the motor is doing its job but the system is unable to determine the position because it can't read the motor position.... maybe. Again, another data point.
 

Maverick6587

Silver Supporter
@ts684 We do have a "list" of Tech 2 owners that are willing to assist with their Tech 2 scanners (link below). Hopefully there is such a person in your vicinity!



Have you tried switching between the 4WD options while on the ground parked and moving? I have a 97x AWD vehicle and it does NOT like being put into drive with all wheels off the ground. I assume that 4AWD operates similarly to an AWD vehicle?
 

budwich

Well-Known Member
I have one other question.... you stated that you originally couldn't get the vehicle into 4WD but that it was in 2WD when you decided to replace the motor. At that point in the replacement, you obviously got the old motor off and had two motors to look at. By any chance did you compare the position of the motor shaft offsets? It probably doesn't matter, as I still think the system knows / can determine where things are IF the connections and motor sensors are good.
 
OP
OP
T

ts684

Member
Ok, either I mis-stated or you mis-read. The original problem was that it wouldn't come out of 4WD. TC motor sounded like it was "cycling" then nothing. "Crow Hop" on turning and parking in my slot was difficult. Then work the next day!! Started in AM with switch in 2WD, amazing, back to 2WD!! Took to dealer a few days later and they couldn't find anything wrong, think they just drove around lot. Since I didn't now hear the TC motor, I replaced. Had a clacking sound at front right axle when supposedly out of any 4WD mode. Thought it might be the disconnect , so I replaced. Now it appears that disconnect only works in 4WD. Think TC motor makes noise in A4WD which I don't think it should. I need to find a better way to hear what is happening.

One thing I forgot in previous post. When I had all wheels off the ground, ignition on, engine off, trans in neutral, switch on 4WD with lite flashing over 4WD, steady lite over 2WD, I was able to turn the rear driveshaft by hand and ALL wheels turned.

Does TCCM just not know what the transfer case is doing??
 

budwich

Well-Known Member
The TCCM can only "read" the position of the motor and what is "desired" by the switch. There is no "feedback" from the TC itself or the disconnects.

As for your "original problem".... I think with the design, IF the disconnects remain locked, regardless of the position / setting of the TC, you will have issues with the front end "doing things" on dry pavement. I think that is because the "rolling wheel" (whether they are driven and passive) will be "locked" to each other and there is only so much the front differential can overcome in terms of "slip" to adjust with different wheel action.
 
Last edited:

budwich

Well-Known Member
As someone suggested, disconnect the motor from the TC. Leave the motor connected to the harness. Place the switch in 2WD, turn the key to on, the motor should activate in some form (or maybe remain in its current position if it "thinks" it is already in 2W). Watch what happens. NOTE: be careful as there is some torque associated with the motor trying to turn. Do the same test, moving the switch to 4WD. Again, observe what happens both at the motor and at the switch lights. This test / action should provide you with observations of the motors operations range along with the "sanity" of the detection system.
 
OP
OP
T

ts684

Member
Ok. With all 4 wheels in air, ignition on, engine off. Turn switch to 4WD, hear disconnect, don't seem to hear anything from TC motor. 4WD lite flashing, 2WD on steady. Turn switch back, huh, sounds like TC motor made a noise!! Turning to 4WD, nothing from TC motor, but turning back it seems to make a noise, unless my hearing is really going. When switch is on 4WD (lite flashing) either front wheel cannot turn if the other is blocked. Guess that means the disconnect is working. Removed TC motor but left connected. Turned switch to 4WD, motor turns, about 120 degrees I estimate. Lite at 4WD still blinking. Turned back to 2WD, oh crap, motor initially backs up but then reverses and goes around 360 degrees, stopping at same position it went to when I switched to 4WD!! By turning switch back and forth between 2WD and 4WD I managed to get back to where it was when I started. I also tried the old motor, made noise but moved very little. Could the TC be jammed, maybe damaging the motor? I am 3rd owner, changed TC fluid at 125K about 1K ago. Looked OK, bit darker than new stuff but not sludgy. Also, at some point, service 4WD lite came on.
 

budwich

Well-Known Member
hmmmm.... :smile:
As suggested, the disconnects and the TC are not "coupled directly in control". The switch tells the TCCM what it wants and the controller executes an operation to each component independantly. Thus, you can get disconnect "lock up" without anything happening at the motor and the tc motor operation and nothing at the disconnects as intended or unintended (failed operation). Your disconnects appear to be working fine.

The observations are helpful but maybe need some more "clarification". You indicate that you put back the old motor and "it made some noise but very little movement".... is this with it totally installed? because you go on to mention the TC maybe being jammed. ???? further with the motor demounted, you should always confirm that you can move the shaft of the TC in some direction.... hopefully fully in one direction and then the other.

Further, in terms of your motor moving directions and stopping at points, you should be able to manually confirm where the equivalent shaft position is on the TC and what that "could represent" in terms of TC mode (ie. 2w,4w, etc).

The full rotation appears to maybe indicate that the motor sensor is having issues although I would expect this to throw some sort of "flash indicators" on the instrument panel as opposed to only the switch. At this point, it would be wise to do some electrical checks with both motors and compare the results. Similarly, then are some basics measurements that can be done on the connector towards the PCM/TCCM.

Having said all this, the reason for the "effort" is that without significant investigation or lack of tech2, it is difficult to ascertain what's happening before and after any operation. Close observations and physical confirmations are needed.
 
OP
OP
T

ts684

Member
I plugged in the old motor but did not install. Turning switch from 2WD to 4WD, pause, then back, produced noise and about 30 deg of movement. The new motor moved about 120deg. The service 4WD lite did come on at some point, I think when I turned switch from 4WD to 2 WD. After wrapping up for the day I thought that I should have tried moving the TC shaft thru entire range. But that brings up another question, is full counter clockwise 2WD? And is this counter clockwise as you look at the shaft? Is there anyway to energize the TC motor other than connecting to car?
 
Last edited:

TJBaker57

Well-Known Member
full counter clockwise 2WD
I spent some time a few nights ago re-reading the operation of the transfer case (linked above) and refreshing my memory. Comparing the graphics of the cam positions shows 2WD not to be at either full clockwise or counter-clockwise but somewhere in between.
 

budwich

Well-Known Member
"Is there anyway to energize the TC motor other than connecting to car? " of course, there is, you just provide 12v to the proper pins AND power to the "brake control circuit" pins. Look at the schematic to confirm what they are.

I seem to recall some form of reset (disconnecting power) of the TCCM (PCM depending on year).... possibly more to do with clearing dash lights if present.

other question: when you have the motor installed (either one) and are you able to get a "stable 2wd" .... meaning solid light on 2wd and the front wheels spinning freely (ie. disconnects not locked)? IF so, at this point, uninstalling the motor and looking at the position of the motor, should provide you with your answer to "where should the shaft offset be sitting?"
 
Last edited:
OP
OP
T

ts684

Member
I plugged in the old motor but did not install. Turning switch from 2WD to 4WD, pause, then back, produced noise and about 30 deg of movement. The new motor moved about 120deg. The service 4WD lite did come on at some point, I think when I turned switch from 4WD to 2 WD. After wrapping up for the day I thought that I should have tried moving the TC shaft thru entire range. But that brings up another question, is full counter clockwise 2WD? And is this counter clockwise as you look at the shaft?
"Is there anyway to energize the TC motor other than connecting to car? " of course, there is, you just provide 12v to the proper pins AND power to the "brake control circuit" pins. Look at the schematic to confirm what they are.

I seem to recall some form of reset (disconnecting power) of the TCCM (PCM depending on year).... possibly more to do with clearing dash lights if present.

other question: when you have the motor installed (either one) and are you able to get a "stable 2wd" .... meaning solid light on 2wd and the front wheels spinning freely (ie. disconnects not locked)? IF so, at this point, uninstalling the motor and looking at the position of the motor, should provide you with your answer to "where should the shaft offset be sitting?"

I was able to get a stable 2WD. That is located 1 "click" clockwise of full counterclockwise. If I keep going clockwise, should the TC go thru A4WD, 4HI, then 4LO?? Where can I find schematic to know which wires to use? (probably right in front of me somewhere)
 

Mooseman

Moderator
A4WD just engages the disconnect. When rear wheel slip is detected, the TCCM moves the TC to 4HI. When wheel slip has stopped for a while, it will move it back to 2WD. That's why when you put it to A4WD, you only hear the disco move.

Links to manuals with schematics are in my signature.
 
OP
OP
T

ts684

Member
If I were to turn the TC shaft manually, what range of movement might I expect? If I remember correctly, always a crapshoot, when I activated the motor, connected but not installed, the shaft did not turn in the direction I expected. Could the TC be somehow jammed?
 

Mooseman

Moderator
It is quite possible that the TC is damaged internally and unable to shift freely, hence the flashing lights when trying to shift modes. If the motor moves fine and the lights are not flashing while the motor is off the TC but it gives flashing lights on the TC, I would assume the TC as the problem. All the position sensors for the TCCM to read are in the motor so if the motor is unable to move to the proper position, it will throw an error.
 
OP
OP
T

ts684

Member
Hope that's not the case. Original problem back in Dec. was that TC was "reluctant" to go out of 4WD. TC motor may have been at fault. Disconnect was another separate problem, possibly caused by grease in actuator.

Lites were flashing when motor was activated but not installed.
 

Mooseman

Moderator
If you can find a scanner able to read all codes, not just powertrain P codes, it would help immensely. An ELM 327 Bluetooth adapter and the Car Gauge Pro app on Android would be able to do this.
 

budwich

Well-Known Member
Hope that's not the case. Original problem back in Dec. was that TC was "reluctant" to go out of 4WD. TC motor may have been at fault. Disconnect was another separate problem, possibly caused by grease in actuator.

Lites were flashing when motor was activated but not installed.
what does that mean "lites are flashing"?
 

Mooseman

Moderator
And do they go out after flashing? Do the lights change when you move the switch again?
 

Online statistics

Members online
6
Guests online
621
Total visitors
627

Members online

Forum statistics

Threads
20,065
Messages
589,034
Unanswered questions
1
Answered questions
2
Members
12,914
Latest member
Magicks72
Top Bottom