Chevrolet Silverado 1500 / 2500 / 3500:

Transfer Case slips out of gear

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# 1  1/19/2012 12:54 AM

stopher8
New member
Registered: 1/19/2012
Posts: 4

Transfer Case slips out of gear

Hello,
I have a 2000 Silverado Z-71, 5.3 with push button 4wd.  The service 4wd light is on and isn't going off. I have read several forums about the selector switch and its problems but they always say the lights are flashing on and off like a short in the switch. My lights are steady. All the 4wd functions seem to be working. I can push any button and I hear the actuator changing the gears. However, three times now in the past 2 days the transfer case seems to go into neutral on its own even though the light still says 2-HI. Driving normal speed, slowing down for a turn or stop light and then attempt to accelerate and that's when all of a sudden its in neutral. The trans selector is still in drive. While still coasting I pushed 4-HI and now I'm back to pulling again. After a few minutes I pushed 2-HI and it went back to 2WD again and all is well. Service 4wd light still on. I went today to have the TCCM codes read but the tech was out for the day. Maybe tomorrow. Any ideas?

Thanks for any help you can offer.
Chris

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# 2  1/19/2012 12:46 PM

TechHelp2
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Registered: 11/24/2009
Posts: 1305

Re: Transfer Case slips out of gear

The TCCM codes are important and are the first step in the diagnosis.

There are service bulletins on the controller, switch and actuator motor. Having the correct code will guide the mechanic to the problem source.

When you get the codes get back to me and I can help you better with the updated information.


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# 3  1/20/2012 3:55 AM

stopher8
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Registered: 1/19/2012
Posts: 4

Re: Transfer Case slips out of gear

Had the codes read today, U1026 and C0323. Tried to clear them several times but they kept coming back.

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# 4  1/20/2012 1:25 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1305

Re: Transfer Case slips out of gear

This is the description for the trouble code CO323

The transfer case shift control module controls the transfer case lock solenoid.
The lock is energized (locking action released, grounding the lock control circuit) during gear shifts and in AUTO 4WD mode of operation. When power or ground is removed from the lock solenoid, (locking action applied), the transfer case motor is prevented from moving. In this manner, the system is capable of providing a 4H and 4L lock-up without the need of additional vehicle power to hold the transfer case in these positions.
This DTC detects an open lock control circuit or an open lock feed.

The U1026 is a communication problem with the transfer case module. Check the ATC fuse in the under hood fuse panel, check all fuses in all fuse panels inside and under the hood just to be safe.

If all circuits check out to be normal then you may need to have the module reprogrammed or if that fails it would need to be replaced.


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# 5  1/21/2012 12:08 AM

stopher8
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Registered: 1/19/2012
Posts: 4

Re: Transfer Case slips out of gear

ATC fuse checks good with test light can check with volt meter if necessary. Where is the ATC located? Is it a module by itself or part of the TCCM? You mentioned reprogramming it. Is this done by the dealer using a Tech 2 or can a local shop do it. If I replace the module will it then have to be programmed too?

Thanks for the help!

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# 6  1/21/2012 2:31 AM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1305

Re: Transfer Case slips out of gear

The trouble code U1026 is a communication problem with the transfer case module and the data buss line.

You would need to take the truck to the Chevrolet dealer to have them check to see if the module is communicating on the data buss line.

If a trouble code of CO550 is stored in the module memory (which you said it is not) then it would need to be replaced.

The reprogramming would need to be done at the Chevrolet dealer; they have the Tech 2 scanner and can put the newest version of the program into the module whether it is the old module or the new one.

If you know of a automotive professional who has the proper scanning tools and programs that can handle the diagnostic and programming procedures then you would be able to take it to them, as long as you feel comfortable with them.

Keep us updated on your progress.


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# 7  2/23/2012 1:01 AM

stopher8
New member
Registered: 1/19/2012
Posts: 4

Re: Transfer Case slips out of gear

Well I took the truck to a trusted repair shop and all of the diagnosis he did pointed to the actuator motor assembly.  After replacing it the new unit didn't work as good as the old one (odd!). He said it kept it in 4-hi all the time. Back to the drawing board. After more troubleshooting he finally decided it was a bad wire and eventually found it. The wire leaving the fuse box under the hood going to the module had been chewed almost in two by a rodent of some kind.  The wire was still hanging on by one strand and that's why it checked good when he tested it but wouldn't hold up while trying to carry amperage. I believe he said this wire powered the lock circuit.

All is well now, thanks for the help and advice!
Chris

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# 8  2/23/2012 4:38 AM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1305

Re: Transfer Case slips out of gear

Thanks for the update, it will help other readers with this type of problem.


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