New to Envoy ownership with PROBLEM 4WD

by **Kazootom** » Wed Jun 19, 2013 10:45 pm

I purchased a used 2004 envoy with 140,000 mile. I took my boat to the ramp the other day and found out I didn't have 4wd and almost buried the envoy trying to get out of the water. I did have AWD only my chance I tried this setting. I came home and found what I believed was the disconnect not working. I disassembled cleaned replaced bearing and seals. (no wear on fork or gears!) I but back together and again have AWD,2wd. When I place in 4wd hi or 4wd low I have motor movement at the transfer case. I have low range but no front wheels drive same is true with 4wd hi. What am I missing?
One last thing. about every fifth start up I have all the indicator lights blink (flash) for 20 seconds then no lights and no noise up front or at transfer case motors.

I am thinking one of three possibilities.
1. TCCM not working correctly
2. Selector switch not working right.
3. Motor on transfer case not working right.

I purchased this envoy from by boss. Super clean wife drove and never used any thing other then 2wd and AWD.

I NEED HELP!!!
Thanks Tom

by **Opeth** » Wed Jun 19, 2013 10:55 pm

Follow this...

http://www.offroadtb.com/articles/tech- ... wd-system/

by **dvanbramer88** » Wed Jun 19, 2013 10:59 pm

If you are absolutely sure A4WD worked, than I would suspect transfer encoder motor or the switch. The front disconnect works the same way in all 4WD modes. You can check that by pulling the motor off of it, and seeing if the actuator moves. You can also manually engage the front disconnect with a socket extension or a bolt for testing purposes.

This flow chart my help you pin-point your problem as well:
http://www.offroadtb.com/articles/tech- ... wd-system/

by **Kazootom** » Wed Jun 19, 2013 11:06 pm

Yes I am positive I have front wheel engagement. I am testing on a grass hill and have wheel spin on rear tires only in 4wd hi and 4wd lo also 2wd. in AWD the tires just grab and go with no spin.

by **dvanbramer88** » Wed Jun 19, 2013 11:11 pm

I'd say transfer case motor or possibly switch not sending signal to transfer case in certain modes.

Like I said, the front disconnect works the exact same way in all modes of 4WD. If you go to A4WD, and it works, than to 4hi, the only thing that changes is the "mode" that the T-case is in, or is being commanded to be in. The front disconnect stays connected when going from one 4WD mode directly to another.

Use the flow chart to confirm that the problem is transfer case related and go from there. Possibly even test the switch with a multimeter to confirm that too.

by **The Roadie** » Thu Jun 20, 2013 1:53 am

Or transfer case clutches fried. Did they change the transfer case fluid religiously every 50K miles?

by **Kazootom** » Thu Jun 20, 2013 7:00 am

I cant answer on the fluid. Fluid was changed when I purchased. The strange thing is that you have low range movement. Meaning very slow ground speed with 4wd lo selected with no front wheel drive. I also have thought about the clutch pack but I all wheel drive. So I assume that that clutch pack works. Does the tccm receive signal from the switch which in turns sends a signal to the clutch pack to engage? If so can the tccm move the position selection on transfer case with out calling for clutch pack lock up? I have a switch that I purchased and can install. I just don't like throwing parts at some thing with out understanding the failed item and effect.
Thanks Tom

by **The Roadie** » Thu Jun 20, 2013 8:52 am

You're right that the operation of A4WD usually means that the transfer case clutches are OK. The encoder motor could be the problem, but then you'd get more error light indications. A mechanic with a high end scan tool could command the encoder motor to go to any of its positions, and diagnose the situation for sure.

For more reading: http://www.offroadtb.com/articles/tech- ... operation/

The Tech Docs section of the web site is a rich resource everybody should absorb.

by **DirtyBacon04** » Thu Jun 20, 2013 3:08 pm

could this just be the 4wd switch itself, which has been known to operate queerly while malfunctioning?

Did you try hitting 'it' with a hammer? ( it = everything)

MY Youtube Channel · by **TBYODA** » Thu Jun 20, 2013 6:09 pm

DirtyBacon04 wrote:?
Did you try hitting 'it' with a hammer? ( it = everything)

Hey don't give away our (Engineer's) secret. Hammer = Calibration tool! ROFL!

by **Kazootom** » Fri Jun 21, 2013 7:56 am

OK update on transfer case no front drive issue.
1. Changed the selector switch. No Change
2. As per a post on GMT I read were people had taken apart the encoder motor cleaned and reassembled. (Did this. was not hard took 30 mintues) No Change.
WAIT!
I took the envoy to my slippery grass test hill and had no 4wd high or 4wd low. Still had AWD
WE live on 10 acres and i decided to take a trip to the back tree line to check on some thing. I forgot after playing on the hill that I had left the selector in 4wd high. When making a tight turn in the tree line I realized I had four wheel drive bind. Well I goosed the throttle on wet grass and have front and rear tire spin.
So I decided to drive around and see what happens. the locking (binding) stayed the same. So I took the envoy for a test run on some pavment in 4wd high. Binding just like you get with the old style new process transfercases with the chain system.

At this point I shifted back to 2wd every thing functioned as it should. I selected all the functions and every thing worked as designed.

So is it possable that just from lack of use of the 4wd and 2wd functions that they need to worked to function again.
Any thoguhts?

Side note I let the truck cool down and did the test again and every thing worked.

Nice! :woot:

by **The Roadie** » Fri Jun 21, 2013 10:07 am

I've heard of systems getting bad from disuse, but I recommend exercising them every month and I thought that problem mostly went away. I'm getting this feeling that not all GMT360 owners were members of trailvoy or GMTN and haven't been doing this, though.

Most of the lazy systems wouldn't slide their disconnect sleeve into position due to congealed grease, but the actuator would extend properly and there wouldn't be an error light. But those folks didn't have A4WD mode working either, so they were different from your behavior.

by **Kazootom** » Fri Jun 21, 2013 2:40 pm

Ok on last thought on this subject. When reading throught the theroy of operation on the transfer case it talks about learning. It implys that with wear the TCCM adjusts to wear. Well if you take a truck like the one I purchased and it has higher miles and you discount the battery for what ever reason would it lose it memory?
If so when you drive it repeatably like I have in 4wd does it learn and then apply the disks for lock up based on the wear that the disks have. I see posts of other people with like issues. I did have the battery discounted a few time in the past couple of weeks. It funny that the 4wd came back after driving in 4wd for a while.
Any thoughts on this possablity.
Tom

YouTube Videos · by **Trail X** » Fri Jun 21, 2013 2:49 pm

I've seen this exact symptom before. It was the encoder motor lock that went bad.

Let me explain real quick.

When in a4wd mode, the motor is constantly monitoring the output of the front drive shaft. If it senses slip, it actively changes the encoder motor position.

In 4lo or 4hi, it commands the motor to a preset position, then activates the motor lock circuit. The motor lock circuit locks the transfer case into position, and the tccm doesn't actively monitor or change anything.

If the lock is not operating, the clutch preload set by the motor can reduce by the motor slipping slightly out of the clutch preload position. Therefore you retain rear drive, but the front clutches are no longer obtaining full torque transfer.

Your cleaning might have freed the lock, or might have fixed a broken connection. I am certain that changing out the motor or motor lock would have fixed the issue.

Keep monitoring it. I wouldn't consider it fixed yet.

by **Kazootom** » Fri Jun 21, 2013 3:14 pm

Thanks for the great info. When I disasembled the encoder motor I found a lot of oxidation in the body of the motor. I cleaned all the elecric connections and greased all the plantary gear sets. I hope this cures the problem. I am going to place in 4wd high a least once a week and keep it free and working. I do use this truck to launch a boat so I will soon know when I get to the lake to pull the boat out.
Thanks every one for the help! Help me now fix my P041 code and I will be a happy camper!
Tom

by **The Roadie** » Sat Jun 22, 2013 1:38 am

JD, I see your point. The motor lock circuit isn't monitored by the TCCM like the other two functions. Hmmmm. And they could have written the code to do that so easily.

by **Kazootom** » Mon Jun 24, 2013 8:16 am

JD, I think I have felt what your talking about. I know that I do have 4wd bind in wet grass. If you goose the the throttle you can get the back tires only to break loose. You really have to try to get this to happen. I was on the boat launch yesterday pulling out a 19 ft I/O boat. This boat weights about 2900 lb with trailer. I was on a slippery ramp and had minor (slight) rear tire spin in 4wd. So I tried 2wd could not move. So I am sure I am not getting 100% lock up to the front.
To get up out of the lake I used AWD and it worked fantastic.

Thanks for all your help. I will keep you posted.
Tom

by **Kazootom** » Mon Jul 29, 2013 3:56 pm

Update: After furture testing I have determended the 4wd lock was not working. As stated earlier from some on the fix is going to be the transfer case shift motor. Well it the problem! I purchased a used motor off e-bay with a 6 month warranty for $51.00 including shipping. I installed in less then 15 mintues. With testing I dont have rear tire slip with out the frounst slipping as well. Problem solved.
Thanks every one for the ideas and suggestions.
Tom

YouTube Videos · by **Trail X** » Tue Jul 30, 2013 10:32 pm

Glad you're operational again.

by **dirty anton** » Tue Aug 06, 2013 11:27 am

I had this same problem a few years back and got a new encoder motor and no more problems. Wish I knew about this back then! Remember trouble shooting for a long time. For someone with similar issues its probably not a bad idea to get another motor and rule this out soon in your trouble shooting. Relatively inexpensive compared to other things in your path of finding the culprit and especially the time. Takes 15 mins to exchange out. Also like said before its a good idea to cycle through your 4 hi 4 lo system every month or so than let it just stay in 2 WD til your next 4 wheelin trip. For some it could be many months or years.

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