1997 GMC 1500 4WD won't engage and just blinks

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Axewhlder

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Sorry this is my first post here but I have to get it out of the way.

I just bought this truck a few weeks ago. As mentioned it's a 1997 350/Z71. When I hit the dash button for 4Hi it just blinks at me. Same with 4Lo. If I put it in neutral (automatic) and try to engage 4Lo I can hear the T-case clunking but it never locks. I checked the fuses by the door for the t-case and the 4wd. Both looked good. I HATE push button 4wd - especially in GM's but I couldn't pass up the deal on this truck.

Any suggestions? Thanks in advance.
 

RHamill

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Front differential actuator is probably bad, it screws in and has a wire harness on the back of it. It should be tan colored. unscrew it with channel locks and have someone engage 4x4 see if it actuates.
 

firefighter_2319

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Front differential actuator is probably bad, it screws in and has a wire harness on the back of it. It should be tan colored. unscrew it with channel locks and have someone engage 4x4 see if it actuates.

i agree, thats the going thing with these trucks
 

Axewhlder

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Any particular noise or action it will do when it actuates? Thanks.
 

RHamill

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It will poke outwards, what it does is push a pellet in the diff and engage the front differential In to 4wd.

sorry I can't go in to a lot of detail typing on my phone is a real pain in the ass hole.
 

buddyp

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I seem to be having a similar problem with my 97 Silverado manual shift.Indicator light says it is engaged but there is a loud clunk/gear clash when I try to drive away.A transmission tech put it on a lift with front axel engaged but did not get any response from the tcase.Says it will be $900-$1500 to find out what it is,Yikes!
 

AirmanSkee

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Axewhlder

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Had the same problem. It was the actuator. Took me longer to get the skidplates off the front of my truck than to switch the actuator. Just a big wrench, unplug it and screw in the new one. Also, the colder it is outside, the longer it will take. Its a "Thermal Linear Actuator", so it heats up and then pushes it out.

http://www.gmt400.com/forum/showthread.php?14282-4x4-button-flashing-Not-fully-engaging-maybe

Here is my thread^^^
Yup. That's it right there. Off to rockauto I go. haha
 
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