Is it in 4wd really?*solved (reset tcase module)

[okaussie]

I have a 2002 CC and noticed the other day that the u joints in the front axle quit "crossing over" when doing a tight turn like turning from the street into my driveway while it is in 4wd. We have had two bad ice and snow storms here in Oklahoma City in the past month so I have been using the 4wd to get around. Never had this problem before.

It has 135k with not apparent front axle problems before
Jacked up right front wheel, started the truck up, tranny in park, put in 4Hi. 4Hi light is on.
First time doing this, I was able to move the right front wheel moved a little then quit. I asume is is okay.
Then shifted the tranny from Park to Drive then back. Checked the wheel again. Now it freewheels.
Put the transfer case into 4Lo. Right front wheel still free.

Took it for a test drive in 4Hi and noticed a little loss of acceleration due to the transfer case being engaged but still did not notice the crossover when pulling into the driveway. Put it in Park and jacked the Right front wheel up again. Still the same problem, wheel freewheels and does not lock.

Do I have problems with the actuator and/or cable to the Front Axle???

If so, is the actuator on my truck under the battery tray?? And where does the cable connect to the front axle???

TIA

Bill

[s10 again]

Bill,

Sometimes it takes a few feet of rolling distance for the front to lock in. When I check for 4wd operation I try to find a dirt or gravel lot turn a circle (Not real tight not good for cvs) and punch the gas. See if the front pulls itself around. A slick hill works good as well. Just give the front a few feet to get locked. If the front is indeed not engaging then there are a few things it could be and each will require its own trouble shooting. First lets make sure there is a problem.


Chris.

[okaussie]

That's why I am wondering if I DO have a problem. I had a 1973 International Harvester 1210 4WD with manual lockout hubs and loved the way it worked. You just locked in the hubs and shifted the transfer case and go. It was all mechanical.

The S10 uses all this new technology and look at all the problems.

Maybe I am looking for a problem that truly does not exist.

How about jacking up one rear wheel and one front wheel, put it in Drive in 4HI and see if the jacked wheels spin??

Since it is not posi trac or have a limited slip differential, I would think that this would work.

What do you think???


TIA

Bill

PS: Supposed to get another round of snow and ice on Monday and would like this fixed, if I do have a problem, by then...

[s10 again]

Bill,

Be careful with the jack trick You can quickly get into trouble even with open diffs. But check your glovebox codes for g80 as that would be a locking diff. But even brake drag on an open diff can cause your truck to come off the jacks.


You could shift to 4wd and drive back and forth a few feet. Leave the truck running shift to park set parking brake and block both in front of and behind rear wheels. Now jack up one front wheel and shift the trans to neutral. Spin by hand the jacked up wheel and see if spins if it does not the front is locked in and t-case is working.

This is safer than applying power to wheels on a truck that is on stands.

EDIT: had it backwards first time I hate dyslexia!


Chris.

[okaussie]

I agree. I will try it and get back to you. It is drizzly and cold right now. Will try it later when the weather cooperates. Should be Saturday. The next storm should be coming in Sunday night.

TIA

Bill

[s10 again]

Glad you understood my post!!! I forgot our trucks don't have neutral on the t-case and trans in neutral will still keep rear wheels locked to the front through the t-case when in 4wd. I'm used to my older Junk (like older Jeeps with front axle dicos) with a t-case neutral then you jack up one front wheel spin it and see if the front shaft spins if so front is locked.

Our front axle disconnect works very much like the older Jeeps that had axle disconnects. It uses engine vacuum to engage the front axle. I'm not sure if ours will keep the front engaged with engine off or not. I had an AMC Eagle 4wd that kicked the front axle off if the engine stalled. A simple vacuum line leaking could cause the system to not work or work intermittently. Later Jeep ditched the system because it was not reliable. They switched to constantly engaged front axles meaning more wear and tear on the front diff,u-joints and t-case.


I use to have a 75 scout II and yes with hubs locked as soon as you hit 4x it was on. When we first got it a friend talked me into putting the front winch bumper against his telephone pole to test 4wd. Well the tires did not spin but it pushed the pole over almost 4" before he started yelling stop. Reading the warning in the glove box explained why. Caution this vehicle is equipped with front and rear locking differentials!!! Between those and the 345 v-8 that pole did not stand a chance.


Chris.

[okaussie]

My 1210 was a super heavy duty 3/4 ton and was built with all the best.
Dana Spicer Front Axle, Chrysler New Process 205 transfer case, Chrysler torqueflite automatic transmission, 3" brake shoes, Warn Hubs, International's own 345 V8 with a 2BBl Holley. It could pull out anything including stuck Ford Trucks. At the time everyone said how the Ford was unbeatable. I was pulling them out all the time and did nothing to alter my truck. Had 16 inch split rim mud and snow tires on 8 lug rims.

The problem was parts were hard to come by and the truck was built so tough that the body could not stand it. I had hood hinge mount problems, tailgate problems, bed problems, etc due to the stiffness of the suspension and a bad body design. It got so bad I had to sell it.

I love my CC but all of the sudden with 135K on it I am seeing problems, like the 4WD issue. Hope it is not going to turn out to be a lemon. It is paid off and enjoy not having a payment. We bought it because had a 97 S10ext cab and it was not big enough for our two Aussies. The CC is big enough with the full backseat for the two of them and the 4WD is a bonus allowing us to go places with them we could not otherwise do.

It has had work done to it that is normal but the 4WD issue is a new one for me. As I posted earlier, maybe I am looking for trouble where it does not exist. I had a noise for about 2 years around the right front wheel and you could feel the vibration in the cab on the floorboard on the passenger front side. Took it in numerous times and no one could find it. I was bound and determined to find it and fix it.
Found the Sway Bar bushings on the right front wheel were worn out and that slop on the bold was causing the noise. Found a broken Sway Bar bushing bolt on the Left side. I replaced the two sway bar bushing kits and the anti sway bushings on the sway bar and interestingly enough the problem disappeared. Took two years and multiple trips to the shop just to find I found it myself. So much for a college degree in automechanics.
Did find that the bolts were a little to long and the nuts did not tighten enough. Had to but a couple of washers on them then use Loctite Blue to seal the nut to the shaft to keep it from working loose.

My point being is that I would like to fix the problems myself given the correct information. It is considerably cheaper and gets me to know my CC better.

It has had no axle problems and want to keep it that way, replaced ball joints, brakes, idler arms, shocks, all that stuff but no problems with the actual axle. It does not get put into 4WD that much living in suburbia but when I need it I need it and if there is a problem it is very frustrating for me.

Thanks

Bill

[Horsehammerr]

You said you replaced the Idler Arm, how about the Pitman Arm ? If you did not , you will be soon ! The Idler has been a major weak point in our steering system . It directly affects the Pitman. When one is bad , you have to change both or you WILL go through the tear it down process again. Suggest using MOOG Problem Solver parts for everything , they are direct fit and lifetime gaurantied. MOOG does not care how many you replace.

[okaussie]

Sorry, I forgot about that. What I should have said was the everything in the front end has been replaced and MOOG was the parts used for all replacements. I was just saying that everything was done except anything to do directly with the axle. It is just odd that now after all these miles that I am, what I think, is having with the front axle really engaging.

I have no abnormal sounds coming from the front end. When I shift into 4WD in the cab I hear the click coming from the T Case. The light on the dash comes on for 4WD however, when making a tight turn now, I don't feel the universals crossover like before. Maybe I am borrowing trouble. Maybe everything is allright.

I have probably use 4WD less that 100 times since I bought it brand new in 2002. Since living in OKC we don't have that much bad weather in which to use it.

I have done the regular maintenance and stuff like that but no problems with the front axle. Have had the fuel pump replaced three times in the last 2 years with the fuel filter but that was the only real out of place problem.

thanks horsehammerr

Bill

[fallvitals]

I just recently thought my 4wd might not be working either. Dad wanted me to drive up this semi steep, gravel, packed snow/ice road. Plenty of tire marks where people had traveled it recently. I was reluncant to give my truck hell just to drive up a hill to stop from walking up a hill....

Anyways, put it in 4 hi, and just spun. It didn't feel like it was in 4wd. I just backed it off and parked where I wanted to to start with. Again, I didn't really try, but it started to bother me after that it acted like it was in just 2wd.

I got home, and I park on gravel, and theres a slight "bump" where my truck normally sets. 2wd wont pull out while ideling in drive.

4 Hi wouldn't either.

4 lo would be like a jack rabbit, so i knew I had no problem with lo.

Put it in 2 wheel, and got some chaulk and marked the transfer case axle. Pulled forward to make sure the axle wouldn't turn (I wasn't sure, lol)

It didn't. So put it in 4 hi, and the chaulk mark moved. So, im assuming if 4 low works great, and in 4 hi the transfer axle is turning my 4 hi is doing just fine too.


I drove back up there a few days ago with only very limited patches of snow/ice on it in 4 hi. Still didn't feel very 4wd-like. The rear tires would start to break traction and spin some, but they didnt spin much, felt like I had a little extra pull, so im sure 4 hi is no problem for me. From what little I have used it, 4 hi doesn't seem all that "powerful", but im reluctant to put it in 4 lo for some gravel road, lol. Seems over kill.

Maybe this helped you some? Your post sounded similer to what I just had, lol.

[okaussie]

When the weather warms up I am going to put it in 4Hi with tranny in park and see if the front driveshaft from the t case is engaged. I think it would be locked, just like the one to the rear end, if not, looks like I have a t case problem. If that is okay, then I would jack up one of the front wheels and try to turn it by hand. If it does not turn, I would think everything is engaged. If it does turn, I think that would tell me that the front axle is not engaged to the driveshaft from the t case. Then we are looking at the vacuum actuator under the battery or the cable from it to the front axle.

All the lights in the cab work like they are suppose to. In 2 Hi it is lit and so on.

We are having snow right now and with the arctic front coming in now the wind chill is +5, so it may be a few days before it gets warm enough to do this. Suppose to snow again on Thursday so it might even be later.

Bill

[okaussie]

Here is what I found out today.

Put it in 2Hi, in Park with the park brake on. 2Hi lite lit. Turned front driveshaft by hand. It also turned the left front wheel that is jacked up.

Put in 4Hi, in Park, with park brake on, was able to turn the front driveshaft by hand and front wheel turned.

Put in 4Lo, all the same as above.

Looks like the t case is at fault.

It never locks up to the front driveshaft and the front wheel turns by hand in any transfer case position.

What am I missing here??

The dreaded vacuum transfer case switch?? Bad encoder motor?

The front wheels acts they are locked to the front driveshaft no matter what the transfer case buttons are pressed.

What next????

More news as it becomes available. film at 11

Bill

[okaussie]

When it is in 2Hi, does the actuator pod disengage the front differential to the front driveshaft?? That way the front driveshaft is disengaged from the front differential AND the transfer case, allowing it to float until 4WD is engaged??

Then when the switch inside the cab is engaged the transfer case engages the front driveshaft and at the same time vacuum is applied to the actuator pod to engage the front differential thereby applying torque to the front differential??

Is this how it is supposed to work???

Bill

[okaussie]

Update:

I jacked up the left rear wheel and left front wheel. Put it in 2Hi in drive to verify rear wheel only. No problem
Put in 4Lo, no front wheel movement in drive.
Put in 4Hi, no front wheel movement in drive.

It appears the entire front wheel part is constantly engaged except the connection between the front driveshaft and transfer case.

It will all turn by hand no matter what the transfer case is in.

I am thinking the encoder motor is bad and when it did go bad the actuator pod was in 4wd at that time and the vacuum to it has kept it engaged thus causing the front differential to stay connected to the front driveshaft. If the encoder motor engages the vacuum to it and the motor died while in 4wd, I would think this would be the case. however, I am not in 4WD. The front driveshaft is disengaged from the transfer case and will not engage.

It is definitely NOT in 4wd, even though the lites on the dash says so.

Now that the entire system is engaged except for the transfer case, I think my gas mileage will suffer with all of that connected.

Where do I go from here???

Bill

[s10 again]

I hope HJ jumps in on this one. I think you might have a problem with the T-case shift motor. But yes once the T-case shifts to 4wd hi or lo a vacuum switch on the t-case is activated to send vacuum to the front actuator to engage front axle.

I know is can take some rolling time before the front axle gets everything lined up to engage. I don't know if the t-case in these rigs need some tire roll to kick in sometimes or not. But I thought if the T-case had not shifted correctly that the led on the shift button would blink and not light up solid .

Hopefully someone with more advanced knowledge of the 4x system in these trucks will chime in.



Chris.

[okaussie]

The 4 Lo light flashes then when I put the tranny in neutral it goes solid. When I go from 2 Hi to 4Hi the lights just switch and stay solid. I did notice something the other night when i was troubleshooting this problem and that was, I put it in 4Lo and when i got up to speed, it automatically shifted into 4HI. It has never done that before.

Is there a way of troubleshooting the encoder motor to verify its integrity. Can I ohm out the 7 pin connector to see if the motor is at fault?? If so, does anyone have a pin configuration and readings to go by???

TIA

Bill

[s10 again]

Oh by the way,

You may have to check the vacuum lines to get the front to kick out. I would first look for vacuum at the t-case switch. from there according to my reading the vacuum gets split. When in 2wd vacuum is sent to one side of the front axle shift motor (actuator) to disengage front axle. Once the t-case is shifted to 4wd vacuum cut from the 2wd line and sent down a second line to the other side. This moves the actuator to engage front axle.

Do your HVAC controls work properly? In searching around on this forum and others. I have found that there were some problems with some of the vacuum switchs mounted on the t-case. They could fail and allow fluid from the t-case to be sucked up into the vacuum system and ruin the HVAC controls.

I think I would check the vacuum lines on the t-case switch not only for vacuum but for ATF as well.


Chris.

[okaussie]

I remember seeing the HVAC threads. I did have a hiss only on the AC positions sometime ago but since went away. Never had a 4wd problem til now.

Are you saying that the actuator pod under the battery has two vacuum lines???

One to pull the cable to the front axle and one to release it???

I am still fuzzy on this type of 4wd. As in one of my earlier posts I mentioned the old style 4wd and really liked it. Just go out and lock in your hubs get in the cab and put it in 4wd. None of this vacuum, cable, electrical stuff. Sometimes the old technology is still the better technology.

I NEVER had any problems with that system and it was a farm truck and in the mud, pulling trees etc. This version of 4wd is a pain.

TIA

Bill

[s10 again]

I thought the vacuum makes a pull pull type set up. Because the t-case switch has 3 lines. But I just found a pic of the switch with labels of the ports. If it is correct one is vacuum supply second is axle actuator third is vent. So now honestly I'm lost again. This makes me wonder if this is like my Eagle and the axle will disengage if the engine stalls. This cause me to have a mishap once. I was playing in mud in our field when the engine shut down kicking out the front axle. Without the front pulling me around a turn I slid through a fence.

Like you said this new junk gets confusing. So many different systems. I have a 03 tracker(Suzuki Vitara) and it uses a air pump to engage the front axle. Jeep(older) and Chevy using vacuum and something uses electric.


My 95 Cherokee is simple shift to 4x and it is there. But there is no way to disconnect the front drive from spinning when in 2wd. As I stated before Jeep ditched the vacuum system in the early 90s due to it being problematic. Unless I drop big $$$ on a lockout hub conversion. I wish I could find one for the s10.

I'm sure someone will chime in here soon and have a good plan of attack.

Paging s10 DR HJ!!!!


Chris.

[HenryJ]

Ok, this whole thread is a little confusing to me, but I'll try to help if I can.

how our s-10's 4x4 works

You have a button on the dash, a module in the right kick panel , a motor on the transfer case, a vacuum switch on the transfercase, a vacuum actuator under the battery, a switch on the front axle.

You push the button, this tells the module what you are requesting. It tells the motor on the transfercase what to do. Once it moves to four wheel drive it activates the vacuum switch mechanically, this sends vacuum to the actuator under the battery that moves the cable to the front axle. Once the shift fork in the front axle moves it actuates a switch to tell the system the front axle / 4x4 is engaged.

Checking the transfer case:
All wheels on the ground and in 2wd you should be able to rotate the front driveshaft by hand. Shift into 4wd and shut it off. The driveshaft should be locked. You should not be able to move it by hand.
Both of those tests done, you know if the transfercase and encoder motor are working.

Checking the front axle:
Start the truck place it in 4wd. This should engage the front axle and transfercase. Shut off the engine. The system should retain enough vacuum reserve to perform the needed tests. Jack up both sides of the front end. Rotate one tire and the opposite side should turn the opposite direction. Rotate both directions and make sure they are not moving independently. If the transfercase will not engage, you will need to find a way to secure the front driveshaft so that it will not turn.
Now restart the engine and switch to 2wd. Shut the engine off. Hold the left front tire and driveshaft. The right front tire should move independently. You will be able to freely rotate both tires in the same direction with out the driveshaft turning.

The binding you are referring to:
The front axle is an open carrier, so we don't get binding from side to side in the front. Each wheel can turn at a different rate. That is what a "differential" is all about. The binding is in the transfer case. Ours is a true 4x4 transfercase , in that it is locked front to rear. Both shafts must turn at the same speed. The binding that you feel is between the two when you make a turn and the front and rear axles traveling different arcs are trying to turn the same speed. The Auto-trac transfercase has a hydraulically operated clutch that allows them to operate at differing speeds. Ours does not.

Our trucks are not a 4wd. Most are 2wd at best, and those with the G80 can be 3wd at low speed. Most times you will only be pulling with one front and one rear while in 4wd.

Clear as mud? Did it help a little?

From what I gather, you have found that the transfercase is not engaging, the light comes on and the front axle is engaging. That would not bode well for your transfercase. Drop the fluid and look for chunks. It is operating the vacuum switch so the encoder motor is moving the shift collar. That means bad gears or chain.
I could be all wet because I was pretty lost trying to find out what works and what didn't. Run the checks above and tell us which is not working, the transfercase or the axle, or both.

[s10 again]

Thanks HJ.

So Our trucks will drop the front axle engagement if the engine shuts off after reserve vacuum is gone?


I think Bill is saying he has no 4x but his front axle is staying engaged even in 2wd.

Could his front axle disco cable be stuck or something else in the dico system stuck or broken keeping the axle engaged. As well as the encoder motor bad keeping it out of 4x?

Do our 2, 4 and 4lo indicator leds blink if there is a problem with the encoder or internal shift problem in the t-case?



Chris.

[HenryJ]

Once the vacuum is gone , yes the front axle will disengage. That is why those with a vacuum leak have trouble getting the front axle to engage. Usually the heater malfunctions as well. That is the first thing we notice.

If the front axle is engaged all the time it is very possible that the cable is corroded and seized.

:finger crossed: I have not personally had to diagnose an encoder motor problem using the lights.

4x4 Different Problems!!!!!!

This one will be very helpful: Transfercase codes

My truck has had issues with it not going into 4 HI. A dealer said it was the selector switch. I told them they were wrong. They replaced it anyway. It quit working again in less than two weeks. I didn't bother with it for months. I had mentioned it on a motorcycle forum in the off topic section almost a year ago now and this was my answer.
FYI Encoder motors don't normally go bad. Sometimes there are components that get moisture inside them corrode including the encoder motor. Usually can be fixed by dissasembly and cleaning. But this is what fixed mine:
1. Turn all accessories off.
2. Disconnect the battery. (BOTH CABLES)
3. Turn the head lights and the key to the on position.
4. Hold the negative and positive battery cables together (grounding them) for 15 seconds.
5. Leave it this way for 1 hour. This is draining computer(s) memory and all residual power.
6. Turn ignition and head lights off.
7. Reconnect battery.
8. Start engine. Let it run for three minutes.(IDLE ONLY) Do not turn anything on. During this 3 minutes your computer is resetting itself and "relearning".
9. Your 4 wheel drive should now work.

I have done this procedure twice and both times were successful.
You'll want to be in 2 wheel drive when you do this.

It sounds like a moisture problem in both the cable and motor could be the issue?

[roadrunner]

HJ has given you pretty good instructions on verification of whether or not the t-case and encoder and actuator are working properly or not. I would only add after reading your posts that the t-case when in either 2hi or 4hi is not supposed to shift to 4lo unless you are stopped and in neutral or park to prevent t-case gear damage. Hence the blinking light and reversion to 4hi if you are in drive or reverse. You can shift on the fly from 2hi to 4hi. I prefer to back off the gas while doing this to help ease harsh or sudden front axle engage/dis-engagement. If you are on a turn the front axle may not lock/unlock immediately. Also there is no second vac line to the actuator for the front axle. Only one and the return is spring loaded for dis-engagement of front axle. There is a procedure for diagnosing electrical problems involving blinking lights but it is problematic at best.
Simply put: 2wd= t-case in 2wd, vac switch inactive, actuator spring holding dis-engaged, front drive-shaft in neutral.
4hi= t-case in 4wd, vac switch active, actuator vac applied, front drive-shaft engaged.
4lo= t-case in 4wd low range, vac switch active, actuator vac applied, front drive-shaft engaged.

Additionally there is an electric switch on the actuator cable near the front axle that controls the led indicators on the dash switch. Inactive=2wd, active=4wd hi or lo depending on encoder position switch activation and tccm control. (tccm located behind left front kick panel in cab)

Hopefully this and HJ's post will assist you. I have had trouble with/replaced everything in this system at one time or another except the t-case. (knock on wood)

[roadrunner]

Thanks HJ.

So Our trucks will drop the front axle engagement if the engine shuts off after reserve vacuum is gone?
I think Bill is saying he has no 4x but his front axle is staying engaged even in 2wd.

Could his front axle disco cable be stuck or something else in the dico system stuck or broken keeping the axle engaged. As well as the encoder motor bad keeping it out of 4x?

Do our 2, 4 and 4lo indicator leds blink if there is a problem with the encoder or internal shift problem in the t-case?
Chris.

Yes when vac is gone the spring load in the actuator returns to dis-engage position.

If Bill's front is staying engaged in 2wd then it would have to be an actuator problem or mechanical problem in the front diff.

Generally the encoder motor itself does not fail. More likely the shift position sensor (which is part of the motor and not sold separately) fails causing faulty shifts or skips or no shift at all. If the dash indicator achieves 4hi and 4lo it is unlikely the encoder is bad.

The shift lights are supposed to blink upon initial start-up. Don't recall how many times but it is listed in the owners manual indicating proper function. There is a procedure to make them blink to indicate trouble codes as well as a procedure outlined in the owners manual to make the t-case "force shift". If there is a defect in the encoder sensor the shift can not be forced as described in the manual. I know because it has happened to me and I was stuck with only 2hi and 4lo available for use in bad weather. Not fun.

Note that the tccm keeps track of bad shifts (faults) versus good shifts. When it hits a certain number of bad shifts the tccm then locks out the system till the problem is repaired or at least until the codes are cleared as described by HJ and in the previous posts he referenced. Hopefully this helps somebody understand the system better.

[s10 again]

Coool guys thanks!

I hope this helps Bill out and I got some advance knowledge on the system in our trucks.

Chris.

[okaussie]

All good information. I think mine is the encoder shift problem. Doesn't make any difference what it is in, the front axle is engaged to the front driveshaft but NOT to the transfer case. I can turn the front driveshaft by hand and the front wheels turn, doesn't matter what position the transfer case is in..

I like the tip of disconnecting the battery and draining all the memory and reinitializing everything. It just might be my problem.

All the lights in the cab appear to work like they are suppose to when I press the corresponding button.

the lights give the appearance that everything is engaged and fine, when it is really not. That is what leads me to believe it could be the tccm being screwed up.

I will do the tip and get back to you all with my findings.

Bill

[HenryJ]

All good information. I think mine is the encoder shift problem. Doesn't make any difference what it is in, the front axle is engaged to the front driveshaft but NOT to the transfer case. I can turn the front driveshaft by hand and the front wheels turn, doesn't matter what position the transfer case is in..

That is the front shift cable or collar stuck. The right front axle disconnects from the differential. The front axle dose not disengage the front driveshaft.

All the lights in the cab appear to work like they are suppose to when I press the corresponding button.

That is the part that worries me, although if the front axle is stuck and the encoder malfunctioning, I guess both problems might exhibit such symptoms.

[okaussie]

Is this over my head??? Do I need to take it in and have it looked at? Does it have so many problems it is too tough for me to tackle? I wonder...

It sounds like to me everything is just GOOFY. I know in computers when bizarre combination of things happen for no apparent reason we say, "if all else fails, reboot". Maybe that is what I need to do. Do the tip above and disconnect the battery and drain all the memory and reconnect and let all the systems reboot.

Seems odd that all of this happened at one time during the last ice storm. Never had a problem before and have only used it less than 100 times during the life of the truck since we bought it right off the showroom floor.

All of this makes me think it is the TCCM and not anything else. I will just do the process of elimination to find out the root cause.

Thanks for all the good info.

More news as it becomes available, film at 11

Bill

[s10 again]

Bill.

I know it seems like a lot and depending on how handy you are with tools it maybe it can be.

I think the front axle problem is separate from the t-case not engaging.

Given how little you are using 4x4 the cable running to the front axle is likely stuck holding the front axle in the engaged position.

The t-case might be a bigger issue if the above reset does not work. I wonder if there is a way to unbolt the encoder motor and manually shift the t-case into 4x to check the inter workings of the case. Anyone have any input as to how and if it could be done if reset fails to work?

Now for that front axle how would Bill check the cable.


And a passing thought Bill has there been any work done on your truck were vacuum lines my have been crossed?
Once you get the system working aging I would engage the 4wd at least once a month or so to keep everything free that may help when it comes time that you have to have it.

Chris.

[okaussie]

Here is the latest. It runs in 4wd now.

Found rebooting the TCCM fixed it. As I said earlier, if things act goofy always reboot.

I unplugged the battery, turned the lights and ignition on , clamped the positive and negative battery leads together and let it sit for about 2 hours. Turned everything off, reconnected the battery. Started her up and let her idle for about 15 minutes.

Tranny in park, t case in 2 hi. Was able to turn the front driveshaft with both front wheels on the ground. It fixed the locked differential to driveshaft problem.

Put the t case in 4HI did the same test. Front driveshaft turned about a quarter of a turned then locked.
Put the t case in 4Lo did the same test. Front driveshaft cont to stay locked.
Went back to 2Hi. Moved the front driveshaft a little, then it unlocked.

Took it for a test drive. In 2 Hi no problems. Put it in 4Hi and felt it lock in. Took a tight turn and felt the u joints crossover. Told me the front axle was REALLY locked in. Moved back on the steering wheel and it went away. Just like it was suppose to.

Drove it home. In the driveway, in Park and 4HI, front driveshaft still locked in.
Put it back in 2 HI, moved the front driveshaft a little and it unlocked.

I think the only times the computers have been cleared is the two times my battery has been replaced. Maybe it was just due to be rebooted.

I think we can close this thread. If it acts up again, I will open a new thread.

Thanks Horsehammerr and all you guys for the great information. I will try to contribute my knowledge when the need arises.

Thanks again,,,

Bill

[roadrunner]

Bear in mind if there is a problem that has not been resolved the shifting problems will return. Remember the tccm keeps track of good shifts versus bad ones and when a certain number is achieved the lockout/up problem returns until the root problem is diagnosed and corrected "rebooting" in this case has just erased memory of the problem from the tccm. Not to throw cold water on ya but you may still have a problem there. I say this because I've been there and done that. I've reset the tccm by removing the kick panel and unplugging it with the ignition switch in off position which achieves the same as the procedure you went through but is easier IMO. Glad it's working for you at present.

[s10 again]

Cool I get to pick up on something new. I hope you did fix the problem Bill however if it returns or happens to someone else I would like to dig a little deeper if you guys are up for it.

Roadrunner,

How did the reset resolve front axle disco not kicking out.? Maybe jiggled whatever was stuck free ?

What would cause missed shifts other than the encoder motor?

Chris.

[okaussie]

To confirm my last post. Just took my wife to chemo and it is now snowing again.

Put all four wheels in the air.
Engine running.
Tranny in park T case in 2Hi
Able to move front driveshaft by itself. no movement in the front wheels
Moved the front wheels independently just like a 4x2.

Put t case in 4Hi. Tranny still in park.
Front driveshaft now locked. front wheels now locked at each wheel.
Put tranny in neutral.
Able to move all four wheels from either driveshaft. Able to move one front wheel one direction and the other wheel goes the other direction, just like the rear wheels. I do not have a positrac or limited slip differential in either axle.
Put in Drive, all four wheels move in correct direction

All the same tests done in 4Lo with the same results.

Took it for a test drive. Found that the u joints don't make the crossover sound when in a tight corner. When I got back home, left it in park and verified front driveshaft still locked.

Also noticed a loss in power when shifting into 4Hi.

I am satisfied now that my 4WD does work

Will find out during the next snowfall, blizzard, ice storm, etc, which could be any day now...

Bill

[HenryJ]

Good to hear you found an inexpensive fix. Hopefully the problem that locked it out was a one time thing and the conditions will not reoccur.

Those who are checking and have the G80 Eaton GovLoc differential will find it behaves the same as your open carrier. It requires more than turning by hand to lock up.
You can test its function by allowing the engine to idle in drive while you have it up on stands. Apply friction (drag a shoe on the sidewall) to one side and after about a rotation you will feel it lock in.

[roadrunner]

Roadrunner,

How did the reset resolve front axle disco not kicking out.? Maybe jiggled whatever was stuck free ?

What would cause missed shifts other than the encoder motor?

Chris.

Most likely an unusual coincidence that the front freed up at the same time as the reset since the front lock is physically dependent on the t-case being in 4hi or 4lo to apply vacuum to the front actuator to engage. Perhaps a stuck cable from the actuator to the axle freed up or a stuck collar from "jiggling". I have lubed the cable on mine several times and found it nearly stuck on more than one occasion which caused me sluggish/no engagement and disengagement. The only other cause I can think of for this would be an intermittent vacuum switch circuit which while unlikely is not impossible if the switch has never been replaced with the updated version and there is any fluid contaminating the shift vacuum system.

Missed shifts (recorded faults) can be caused by the encoder motor, shorted wiring, dash switch, and even by the indicator sensor/switch on the front cable by the axle not to mention the tccm itself. Some may doubt this but all these have happened to me personally. Hope this information is helpful to you.

[s10 again]

Cool.

So if Bills front axle disco was stuck engaged in the 2wd selection would that have counted as a missed shift. I did not know there was a switch to confirm axle engagement/disengagement. so I indeed get to learn more on how these systems work.



Chris.

[roadrunner]

Cool.

So if Bills front axle disco was stuck engaged in the 2wd selection would that have counted as a missed shift. I did not know there was a switch to confirm axle engagement/disengagement. so I indeed get to learn more on how these systems work.

In my experience YES it would count in the tccm as a shift fault since the switch on the front axle would not verify what the rest of the system says should be going on. The switch is located on the axle end of the front shift cable and has a set of wires attached to it. I encountered this problem as well when my mounting screws came loose that hold the actuator diaphragm to it's mounting bracket under the battery carrier. End result system in 4 wheel drive and axle NOT engaged thus switch says no shift and recorded as a fault or bad shift (same as a stuck cable). And yes the screws can loosen sufficiently to prevent front axle engagement.

[s10 again]

Interesting thanks for taking the time help us understand things.


Chris.

[roadrunner]

Glad to help out. Well worth it if it'll save somebody else some frustration.

[HenryJ]

...Found several cracks in the vaccuum lines in the engine compartment by the ABS next to the driver's side fender panel. Replaced the affected hoses and the SES light reset. No more error lights.

the thing shifts into and out of 4WD just like it is suppose to. Think that my previous thread regarding the 4WD problem was related to the vaccuum leak.

Everything is fine now and shifts like it is suppose too.

Bill