Novice Attempting TC & Disconnect Service, Help?

Mooseman

Moderator
There are two types. One for 4x4 and another for AWD. The latter has less wires as there is no brake in it. So if you look under TB's and Envoys for one, you'll be fine.

The way it works, the TCCM disengages the brake in the encoder motor, moves the shaft to the appropriate position and re-engages the brake. When you put it in A4WD, you should just hear the disconnect in the front engage. Then, when you next move it to 4HI, you should then hear the TC move. If you go from 2HI straight to 4HI, you should hear both consecutively.
 
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NotAMechanic

Active Member
When you put it in A4WD, you should just hear the disconnect in the front engage. Then, when you next move it to 4HI, you should then hear the TC move. If you go from 2HI straight to 4HI, you should hear both consecutively.
Interesting. When I click from 2Hi to A4wd, I definitely hear a motor. When I then click it to 4Hi, I hear the same noise. When I try to do the last one, I hear nothing and it waits and waits and waits and gives up.

I don't know if I've tried going straight from 2Hi to 4Hi.

Maybe both motors are going and my ears are just thinking they're both from the front.

Or maybe it's not even engaging the front at all, and hearing the same noise again from A4wd to 4Hi is it trying the front again.
 

Mooseman

Moderator
When I try to do the last one, I hear nothing and it waits and waits and waits and gives up.
Do you mean trying to put it in 4lo? It won't work unless you are moving a little.
I don't know if I've tried going straight from 2Hi to 4Hi.
Try it. You will hear two noises and you will notice the differences (the second one on the TC is longer)

Maybe both motors are going and my ears are just thinking they're both from the front.
I say it's your ears :biggrin:

Or maybe it's not even engaging the front at all, and hearing the same noise again from A4wd to 4Hi is it trying the front again.
You can test the whole system, including the disconnect as per this:
4WD not working? Step inside.
 
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NotAMechanic

Active Member
Do you mean trying to put it in 4lo?
Err, yes. 4lo.

You can test the whole system, including the disconnect as per this:
It's on my list, but, it's been snowing constantly and cold.

...

Friday I did drive it around out of town. I pulled into an ankle-deep snowy angled parking spot, and then tried to reverse out in 2Hi. Half-second of tire slip and then traction control would kick in and not let me spin tires for 2 or 3 seconds. It was such a mild amount of snow I was just about certain if it would've just let me give it gas it would've dug itself out, but, nope, traction control kept shutting me out. Ended up having a family help push me back since they were there at the time and might have been alone when I was leaving. (No attempt to put it in 4wd). Couldn't figure out how to turn off traction control though.

Sunday I did have a friend take it for a drive with me to an empty snowy parking lot.

2Hi - Got stuck on a very small incline (Jean-Luc Picard Tires)

A4WD - Gave it a few revs and then it coughed up the 4wd error light. Ignition off and back on again, stayed off. Never got the light to retrigger.

4Hi - Maybe worked? Was hard to tell, we toggled between 2Hi and 4Hi a half-dozen times and it seemed to be a lot easier to reverse up a snowy incline better in 4Hi, but, again was hard to tell with the tires.

4Lo - Definitely was in a low gear. Whether all 4 were powered is questionable, but it positively charged ratios. But this should be 100% proof that the TC motor is working, no?

So, maybe it's all working perfectly. Maybe at worst, not all the signal wires to the TC are good. But if 4Lo engaged then motor must be fine.

When I get it somewhere dry and have some spare time, I'll go through the proper 4wd diagnostic procedure.

...

Other than that, I gotta look up how to reset the tire pressure warning system (not the same as the trailblazer apparently) and reprogram the FOB (again not the same as the TB).
 

Mooseman

Moderator
Couldn't figure out how to turn off traction control though.
Just under the shifter lock button, there is a small button. Push and hold it and it will eventually turn off traction control and Stabilitrak.

Could be the disconnect as the transfer case seems to be working. Put it in 4hi and jack up the right front tire. Try to turn it. If it does, likely it's the disconnect or worse, the intermediate shaft.
 

TollKeeper

Well-Known Member
I completely forgot you could do that.

Put the truck into 4hi. With the ignition on, engine not started, Jack up -1- of the front wheels, and try to spin that 1 wheel. No spin, 4wd is engaged.
 
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NotAMechanic

Active Member
With the ignition on, engine not started,
That was my next question.

The parking pall doesn't prevent things from rotating? I guess, if the transfer case has the front disconnected from the tranny, that makes sense that it could rotate.
 

TollKeeper

Well-Known Member
If the transfer case is engaged, then it's directly connected to the rear diff. If the rear is on the ground, and one front wheel is on the ground, and one in the air, it should not spin.

If it does spin, look at the front diff drive shaft. If it is spinning, then you know it's something to do with the TC. If it's not spinning, then you know it's either in the diff, or the disconnect.
 

Mooseman

Moderator
All this is in the linked post I posted earlier, step by step.
 
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NotAMechanic

Active Member
https://gmtnation.com/forums/threads/4wd-not-working-step-inside.106/ - "Now is the time to make a post detailing all the steps you followed in this guide as well as any other observations made."
I put it in 4Hi. I turned the car off but left the keys in ignition. I lifted the driver's tire. I could rotate it maybe 5-10 degrees but no farther. Stunning success.

I put it in 2hi. I could spin the tire easily. Just to confirm the tire wasn't stuck on something.

I had someone else listen for noises. Turns out the transfer case motor is super quick, almost just a click, whereas the disconnect actuator gives a couple second whirl.

Then I confirmed it was in 4wd by finding a frozen parking lot and then a frozen gravel yard and goofing around for 10 minutes.

I guess I fixed it right the first time. Just the disconnect. Not the transfer case, and gladly not the diff.

*dusts hands*

Thanks everyone! My first adventure into the realm of not-paying-someone-to-do-your-mechanics was relatively painless.

Who pays for the forum and where can I drop a bill or two?
 

TollKeeper

Well-Known Member
Look at @Mooseman 's signature. Its there on how to donate.

Then I confirmed it was in 4wd by finding a frozen parking lot and then a frozen gravel yard and goofing around for 10 minutes.
Be careful when doing this. The power steering shaft is known to sheer doing this. There have been a few people on the forum to find this out the hard way..
 
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NotAMechanic

Active Member
Look at @Mooseman 's signature. Its there on how to donate
Was lookin' just for an email addy directly, not an account. Can't find one, just, membership type stuff, and, I don't need a membership, happy to just throw some cash.
 

Mooseman

Moderator
We certainly appreciate any donation to keep the site going. As per our big boss:

If anyone wants to donate, they can PayPal us at payments@423network.com anytime.

Thanks!
 
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NotAMechanic

Active Member
Super. Off it goes.

...

What do I do with an extra transfer case? Sell it on ebay or Craigslist or something? Is it worth anything? It's been too long to return it to the junkyard. Have the new gasket for it too :/.
 

Mooseman

Moderator
You could open it up, gut it and make a couple of planters :dielaugh:

Seriously, you could try CL, never hurts to try and it's free. After a while, when you're tired of seeing it, bring it and other scrap metal to a recycler and get a little bit of cash. Or do like the rest of us and hoard it "just in case" :biggrin:
 

TollKeeper

Well-Known Member
We did not hoard, we pre purchase knowing the history of the brand! At least it's not a Ford where we just need to purchase a spare vehicle.
 
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NotAMechanic

Active Member
Or do like the rest of us and hoard it "just in case"
I have a whole home full of Just In Case. And a storage locker.

Heck, the Envoy itself was hoarded for 2 years as a Just In Case.

How many broken air compressors do I not need? At last 6, better keep them. And what happens if I need a 4" x 20" strip of plywood? Buy a whole new sheet? Nonsense. A freezer full of ham? It was on sale. No it doesn't matter if I don't really eat ham that much, I'll learn.
 
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NotAMechanic

Active Member
I have a quick question, as I'm not 100% sure about the operation of the 4x4 or if there were different versions on later models (mine is 2009).

How smart is the 4hi?

Is it just, full on in lockstep, or, does it have power increments determined by a computer? Does it function like an AWD or is anything other than 2hi only for offroading and snow-covered roads?
 

TollKeeper

Well-Known Member
4hi is full on lock in. If a back wheel is turning, a wheel in front of turning at the same speed.
 
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NotAMechanic

Active Member
Gotcha. So, just not suitable for pavement at all.

I guess I don't really understand what the StabiliTrak system thing is then.
 

Mooseman

Moderator
It's two things. One is traction control where it will limit wheel spin by easing the throttle and applying the brake to the spinning wheel. Stabilitrak itself will, in theory, bring the vehicle back straight if there is loss of stability (ie: fishtailing) by also applying brakes and easing throttle according to.steering input.
 
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NotAMechanic

Active Member
Bump. Me again.

Well I wanted to sell it, but, instead I just kept driving it to get some joy out of the work I put in.

Until now. Few questions.

I took it in for an oil change, they did that, reset the light, and reset the tire pressure warning.

However, maybe coincidence, but now it's not shifting into 4x4, maybe.

- 2WD to Auto4 = Worked fine, lights indicate such.
- Auto4 to 4Hi = Never engaged, LED fails and stays in previous mod.
- Auto4 to 4Lo = Engaged and worked, was definitely in low.
- Back to 2WD = Won't disengage from Auto4 anymore. Even turning the car off and back on again.

So... is something broken, or does shifting into 4Lo indicate both motors must be working?

I haven't re-done the jackup 4wd test procedure yet, as the lights aren't indicating it's working anyway.

Also, tires are kinda bald, could use a set of winters. Saw some for sale already mounted on rims, but guy said they're only good for a 2002-2006 Envoy because even if they fit, the 2009 has wheel sensors or something?

True? That would be in the rim, not the tire, right? So if I wanted the tires I could still take those? What happens if I run without wheel sensors? What's the consequence?

Thanks all.
 

HARDTRAILZ

Moderator
I think he means tire pressure sensors and you can swap tires on to your wheels and your tpms sensors will still work fine
 

Mooseman

Moderator
It could be the switch. With the ignition off, turn the switch a bunch of times the clean the contacts.

When you have it in 4auto, try spinning the tires to see if it engages the front wheels. If it does, then your disconnect and encoder motor seem to be working correctly. I would try replacing the switch since the other modes seem to work and not 4hi.

For the wheel sensors, go ahead and get those wheels and tires. You'll just get the TPMS light (and a message in the DIC if it's an LT) that it's not working. Or just get yourself a set of sensors and relearn them.
 
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NotAMechanic

Active Member
Seems to be the switch, as, it snowed 6" last night and on bald all-seasons I could still move around.

Can anyone confirm for me that rims from a 2002-2006 fit, bolt-hole-wise, on my 2009? Or where I would go to look that up?
 

TequilaWarrior

Well-Known Member
Seems to be the switch, as, it snowed 6" last night and on bald all-seasons I could still move around.

Can anyone confirm for me that rims from a 2002-2006 fit, bolt-hole-wise, on my 2009? Or where I would go to look that up?
I'm 99.9% sure that all the wheels are the same from year to year. Not sure on changes for wheel diameter which may be an issue for brake caliper clearance. If the 02-06 wheels are 17" - there should be no issue.
 

Mooseman

Moderator
I am 100% sure they will fit but they MUST be 17" if you have the bigger front brakes (V8). I have the wheels from my old '02 on my '07 which has TPMS system but I didn't put on sensors. A piece of black tape over the light took care of that :biggrin:
 
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NotAMechanic

Active Member
8 month bump.

So, this Envoy I've been fixing up to sell... instead I drove. (And I indeed did buy those winter tires and rims I mentioned previously). Also my other vehicle hit a deer and required me to learn more than I wanted to know about it, so I tinkered away at that while I drove the Envoy.

I also bought a pair of 50-year old classic cars for scrap metal price, and a 16' trailer, and hauled them around with the Envoy, so, actually using it for more than just a commuter vehicle.

However...

Today, winter again, I finally got around to diagnosing the last issue I was having, after driving the Envoy for 4 months after you guys all helped me replace the front disconnect (it worked great from November-March). That it wouldn't go into 4-hi anymore.

Well, I lifted up the front driver's side tire, put it into 4-hi, heard the shuck (transfer case) and the whirrr-cluck (front disconnect) so both actuators move... but the tire spun freely.

I crawled underneath, the front driveshaft (the thing between the transfer case and the front diff?) was spinning when I was spinning the wheel.

From the famous "4WD not working?" thread... https://gmtnation.com/forums/threads/4wd-not-working-step-inside.106/ ... and advice above... spinning tire + spinning driveshaft = the transfer case is shot? Someone want to idiotproof that for me to confirm I'm not misdiagnosing it?

...

The good news is that in the 4 months it was working, it passed its out-of-province inspection, (a one-time checklist of "yep, all systems work"), so, I could sell it to someone and they can still legally drive it in 2-hi all the time. So maybe I will.

But otherwise, looks like I'll have to replace the transfer case. The other good news is that I originally thought I'd have to do the TC and the FD both, so I've been sitting on this transfer case I figured I would never use, for 8 months. And two pints of smurf blood I'd already traded a testicle for at the dealership.

The bad news is that I have no idea what I'm doing (it's been a year since I got it from the junkyard, and I was ignorant enough I ended up disassembling the end of the transmission instead of the seam between tranny and transfer case).

Anyway, if I can follow directions correctly and I've made the correct diagnosis, wish me luck :/
 

TJBaker57

Well-Known Member
wouldn't go into 4-hi anymore
If it doesn't go into 4hi with the shift indicator light remaining on in 4hi then the front driveshaft spinning does not necessarily mean the Transfer Case is shot. Because if that light is not on solid in the 4hi position there's a very high likelihood you are not really in 4hi and of course the front driveshaft will spin when you spin a front wheel,,,,,,,,because you are not in 4wd. I would recommend reading up on the encoder motor and how to remove it and manually shift the transfer case with a good pliers and THEN see if the front driveshaft spins. You may find that what you have is a bad encoder ring inside the encoder motor. A very very common failure for these vehicles. Most folks replace the entire encoder motor though it is possible to replace only the encoder ring inside if that is what the actual problem is.
 

budwich

Well-Known Member
As suggested / mentioned, what was the status of the light on the shift indicator / switch? If it was flashing, odds are high that the shift motor was not "fully functional" even though your ears were indicating "some operation". As mentioned, the shift motor can be replaced but it can also be disasembled / checked. The interior has lubricant which can get on the "wipers" of the contacts along with the resistance ring itself which then will cause problems in the system not being able to determine the actual position of the motor and the transfer case... the case itself has no "feedback" to the system to indicate "physical success" to the controller outside of the shift motor feedback.
 

TJBaker57

Well-Known Member
So you have disassembled a front disconnect I see...if you're curious about the insides of a transfer case encoder motor here is a thread where I replaced my encoder ring. Yes, it is cheaper to replace just the ring if you know the motor is sound, but it may be wiser to replace the whole unit as most all folks do. (I've never claimed to be like most folks :wink: )

 

Mooseman

Moderator
You definitely need to test the encoder motor before condemning the transfer case. Put it in 4hi and switch off the ignition. Remove the encoder motor and move the shaft with a pair of pliers. At the different detents, try that same test with a wheel off the ground. If it now locks the driveshaft, then it's likely the encoder. With the encoder removed but still connected, turn on the ignition and switch to different modes while watching the motor for proper movement.
 
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NotAMechanic

Active Member
As suggested / mentioned, what was the status of the light on the shift indicator / switch?
It never clicked into 4hi. It attempted to, and then gave up and stayed in 2hi.

I'm almost positive I ganked an extra encoder motor when I pulled the spare transfer case. That would be delightful if it's just a stupid motor and not 80 lbs of steel and oil.

You guys are wonderful. I'll try that next chance I get and report back.
 

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