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bobkyllo 
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Joined: 14 Sep 2009
Location: minnesota
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 Topic: Chevy service 4x4
Posted: 26 Oct 2020 at 6:03pm |
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I've got a customer in with a 2001 Chevy Silverado 1500. They complained it had the service light on. I got it in and everything worked great on the hoist. I shifted between all the modes probably a dozen times. No problem at all. Guess I can't fix it.
So I back it out took it around the block. At the stop sign I clicked it into 4x4 hi. Bam the service light come on right away. I can not for the life of me get it out of 4 high. I tried forwards I tried backwards I cycled the key. Nothing worked.
I pulled some codes and I get c0300 for the rear speed sensor signal and I have c0374 which is for the transfer case motor.
I'm looking for some direction for tomorrow morning. I'm guessing possibly some bad wires at the case? Perhaps something related to the speed sensor.
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Thad in AR.
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Joined: 12 Sep 2009
Location: Arkansas
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Posted: 26 Oct 2020 at 6:13pm |
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I’m no help but following. My service 4x4 light just came on
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DiyDave
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Joined: 11 Sep 2009
Location: Gambrills, MD
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Posted: 26 Oct 2020 at 6:19pm |
The older ones I am familiar with, had scads of vacuum pots that controlled shifting. Diaphragms in them went bad. Might not be the same with the newer ones, don't know... 
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Hubert (Ga)engine7
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Posted: 26 Oct 2020 at 7:27pm |
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I would suspect the xfr case motor or the already mentioned wires/connections.
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Just an old country boy saved by the grace of God.
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steve(ill)
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Location: illinois
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Posted: 26 Oct 2020 at 8:27pm |
The code means the front drive shaft is not turning at the proper speed... Rear wheel slip is what the computer sees... Either the wire is bad, speed sensor bad.. or transfer case drive to front axle is bad..
C0374 Description The transfer case shift control module senses rear slip. After several attempts of applying torque to the front wheels, by activating the encoder motor, the transfer case still sees a difference in speed between the front propshaft speed sensor and rear propshaft speed sensor. The transfer case shift control module is unable to correct sensed wheel slip for 10 consecutive seconds.Read more: https://www.autocodes.com/c0374.html
skip to the 2:00 minute mark about possible internal problems in tranfer case
https://www.youtube.com/watch?v=kuz3mQSTy58
Edited by steve(ill) - 26 Oct 2020 at 8:29pm
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Like them all, but love the "B"s.
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shameless dude
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Posted: 26 Oct 2020 at 11:31pm |
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i have the same thing on my 2003 burb, my mechanic got something for it, but can't remember what it is. guess he's gonna put it on tomarrow, i'll report back as to what it was/is. he said what ever it was that it's a common thing on those years Chevy's.
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Thad in AR.
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Posted: 27 Oct 2020 at 6:13am |
 shameless dude wrote:
i have the same thing on my 2003 burb, my mechanic got something for it, but can't remember what it is. guess he's gonna put it on tomarrow, i'll report back as to what it was/is. he said what ever it was that it's a common thing on those years Chevy's. |
Thanks and please let us know.
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Brian Jasper co. Ia
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Posted: 27 Oct 2020 at 3:26pm |
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Somewhere around that time frame they tried to use a stamped steel tone ring for the front drive shaft. It didn’t have a sharp enough profile to produce a steady pattern from the sensor. The fix then was to replace the tone ring with a powdered metal style tone ring.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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bobkyllo
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Posted: 27 Oct 2020 at 10:20pm |
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You guys keep telling me it's not seeing the correct speed for the front wheels. I understand that, and that's what I read from my service info.
What I don't understand is I cycled the case between all the different modes many many times on the hoist with the motor both running and with the engine off key on. No wheel turning at all and it working flawlessly.
I then took it around a couple blocks in two wheel drive. Thought I might hear something wrong. Sounded pretty good. I come to a complete stop, I pushed 4 high and instantly it went into a fault. The service 4 wheel drive come on and I can not get it out of 4 high.
I understand a stamped tone ring can affect it. But I was not moving when it went into fault mode.
So my problem in no way can be a tone ring or the difference between front wheel speed and rear speed.
I've either got a bad motor, bad wires, or bad switch.
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DaveKamp
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Posted: 27 Oct 2020 at 11:32pm |
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Probably unrelated, but my '99 1/2t Silv munched it's 4L60 (lost reverse ring). On rebuild, the trans service had to pull the T-case, so it got a look-inside, and aside from substantial chain-stretch, there was a spot inside the case where the shifting mechanism tended to wear into the case casting. They had an 'insert kit' that went in it's place to resolve the case wear, and a new chain. He mentioned that the shift rod wear would eventually cause it to do something weird and pop that code, and supposedly, crack the case at the wear spot. <shrug> Dunno, as after dumping 3 grand into that repair, I drove it 4 miles down to my dad's house and back pulling a car hauler with 1400lbs of dimensioned lumber, and had it burst a brake line... the ABS pump promptly and efficiently relieved the entire system of all fluid, leaving me rolling into a (opposing traffic does not) stop sign with no brakes... and no, the lame parking brake had no substantial ability)... The engine, transmission, and T-case brought $1500... the rest got shredded...
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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steve(ill)
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Posted: 28 Oct 2020 at 9:00am |
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Im not sure on the Chevy, but on a FORD, when you push the button for 4 x 4 it signals the transfer case motor to SHIFT.. At the end of the stroke it hits a switch and tells the computer it has gone into gear, and it signals the front axle to lock in also ( by vacuum)... If the transfer motor does not go FULL STROKE, you might get a " 4 x 4 error" ??
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Like them all, but love the "B"s.
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