1997 Chevy Suburban Issues with it tring to shift into 4 lo

1997 CHEVROLET SUBURBAN
150,000 MILES • V8 • 4WD • AUTOMATIC
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MELAMOM2
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Need to know what would cause it to shift from 2 wheel drive to 4 Hi to 4Lo by its self going down the highway at 60 mph. It made big clunck and then would not accelerate. pulled it off the side of road and put it in park and made horrable grinding sound.Waited about 10 min. and started again pushed 2 wheel drive and another big clunck then could go. Was not wanting to shift right from 1 to 2 would really bog down. Parked untill can figure out problem. Help is the only family vehicle.
Thank you.
Nov 11, 2009 at 9:28 AM
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RACEFAN966
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Well it sounds like you may have a transfer case control module (tccm) problem. So do any of the lights for the 4wd light up? Have you check the 4wd fuses? Were any blown? Let me know what you can so we can do some testing. Can you have it scanned for the TCCM to get codes from the 4wd system to help figure out what might be wrong?
Nov 11, 2009 at 10:26 AM
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MELAMOM2
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No fuses are blown. The lights come on at start up but then all of them go out. Can I unplug this TCCM and still be able to drive vehicle the 30 ml. to the shop to have it tested?
Nov 11, 2009 at 10:35 AM
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RACEFAN966
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Ok the TCCM is located under the dash om the steeing column support bracket. Now what you can do is test this your self. Locate the orange wire or term number 13 and make a jumper wire and connect it between the orange wire and ground. Now turn the key on engine off and the 4wd lights should blink. If all the 4wd lights only blink once then there is no codes stored. Now if there is codes stored then the lights will blink them with 3 second delay's between codes. You just count the blinks. If it is a code 1 then it will blink once and wait 3 seconds and blink it again. Now if there is code 1 and 2 then it will blink once wait 3 seconds and then blink twice and will wait 3 seconds and repeat it. Once you have the codes (write them down). Once you are done then I would like you to clear the codes to do this you simply remove the t-case fuse 20 amp and wait 40 seconds to reinstall then after you reinstall the fuse turn the key on engine off 5 times codes will be cleared. Get back to me with the codes and we will see what the system can tell us. The t-case fuse should be in the under hood fuse box. Let me know what code or codes you find.
Nov 12, 2009 at 9:42 AM
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MELAMOM2
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No codes. Pulled t case fuse husband started with fuse out and removed from park . Now is blowing fuses and stuck in Netural. When we jumped wire and turned on vehicle. We got a clicking out of something sounded like a relay clicking could not find the relay. Moved wires around and it stopped and will not do it again.
Nov 14, 2009 at 6:44 PM
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RACEFAN966
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Ok is this a 1 ton? If so then is has a transfer case relay on the right firewall.
Nov 17, 2009 at 9:53 AM
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MELAMOM2
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No it is a 3/4 ton and it has no fuse under hood for the t-case. Shut vehicel off for 24 hrs. and is now in gear. What is going on keeps blowing t-case fuse?
Nov 18, 2009 at 7:31 AM
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RACEFAN966
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Well it seems that the transfer case module that is on the steering column bracket is bad. The T-case fuse 20amp is what powers the module that is all it does.
Nov 18, 2009 at 10:12 AM