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Old 02-06-2013, 02:20 PM
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Default 1998 blazer wont disengage from 4wd

Ok, I ve got a 1998 chevy blazer 4dr 4x4 ls. It will go into 4hi and 4lo with no problems. When I try and go back to 2wd it'll just make the clicking noise and stay in 4wd. I do have a front fifferential leak but I made sure that the gear oil level is correct so I don't believe that is the problem. Also, if I let the blazer sit for an hr or 2 and turn the key to run and hit the 2wd button it WILL go into 2wd until I have to use the 4wd again then its back to the same problem. Would anyone have any idea as to what the problem is? If you need any more info just ask. And thank you everyone in advance
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Old 02-06-2013, 04:06 PM
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are you sure that its just not your front diff hanging up?

what i am saying is that the transfer case could be doing what it needs to, as in going back to 2wd, but the front axle is staying locked in. that would be an issue with the cable and actuator that are under the battery tray. you could have a bunch of crud and gunk in the cable putting it into a bind and not letting the axle unlock.
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Old 02-06-2013, 07:31 PM
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I would say your TCM is being reset when the vehicle is turned off. Does it really need to be off for 2 hrs. Pulling the fuse to the 4WD resets the TCM. You can also try that instead of waiting 2 hrs. Check the TCM behind the passengers side kickpanel. The blazers tipically leak rainwater directly on that module and connections become corroded. Its a shot in the dark. What does the button do when you push it. Typically it blinks as it transitions from 4WD to 2WD or visa versa. Those lights get feedback from the TCM as to what position the motor encoder is in. There is also a vacuum side to this mess which controls that front differential cable. I dont know how the two talk to each other. There is a vacuum switch on the firewall of the engine compartment. I dont know what tells that switch what to do. Maybe that signal also comes from the TCM. Check the corrosion on those TCM connections - easy to do. If corroded get a small tub of dielectric grease from NAPA and lube it up. I had to cover my module it was getting that wet. Water runs down the harness directly into the connector. I searched several junkyards and almost ever module I found showed signs of getting wet.
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Old 02-06-2013, 07:55 PM
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Check to see if the actuator under the battery tray is receiving constant vacuum (i.e. t-case vacuum switch stuck open).
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Old 02-06-2013, 08:08 PM
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I will check into the module corrosion. Also when I push the 2wd button it does blink and you can here clicking like its wanting to go into 2wd but it doesn't and stays in 4wd. Yes, it litterally needs to be off for a couple hrs for me to be able to get it back into 2wd. Unhooking the battery and/or pulling the 4wd fuse does not help at all. Ill also check into the cable binding up or possibly needing lubed up. I'm also gonna run the codes on the 4wd system also. I didn't even know that you could do that until I found the link earlier today. Also, when is the actuator under the battery tray suppossed to have vaccuum?
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Old 02-06-2013, 09:13 PM
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when you are in 4wd. otherwise it shouldnt have any vacuum.
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Old 02-06-2013, 09:36 PM
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Ok. What about when I push the 2wd button? Should it lose vaccuum when I push the button or when it actually goes into 2wd
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Old 02-07-2013, 02:14 PM
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Originally Posted by aaronjohn20 View Post
Ok. What about when I push the 2wd button? Should it lose vaccuum when I push the button or when it actually goes into 2wd
yeah, when you press the 2wd button it should lose vacuum. when all the vacuum is gone and its at regular atmosphere then the front axle has a chance to unlock. sometimes it takes it a little bit to actually unlock. just drive it and you might hear a thump or something to indicate that the transfer case has unlocked and usually by the time that happens, the front end already did. you can check it by parking it on flat ground, car in park, engine running, and jacking up the front passenger wheel. spin the wheel by hand, if it turns, then its unlocked, if it doesnt turn, then its still engaged.
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1998 Blazer LT 4.3 4 Door <--work truck AKA The Work Horse
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"Built, not bought!" Ya gotta love the pride that comes with building your own rig!
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Old 02-07-2013, 02:14 PM
 
 
 
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1998, 2wd, 4wd, 98, 99, back, blazer, change, chevy, disengage, drive, located, stay, tcm, wheel, wont


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