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4x4 Quit AGAIN!!

1525 Views 13 Replies 4 Participants Last post by  c0rey
Well working on a 90 chevy again. I just put new halfshasts in it. Worked good for a couple times i needed it. Only used to get outta light snow. Went to put it in 4x4 today and nothing. So I pulled all the connections on the diff to check them out. All turned out fine. Front driveshaft is spinng. I had in in 4x4 on gravel rd after like 50 mph there is a noticable vibration! When its in 4x4 the halfshafts dont move and the 4x4 light inside the cab doesnt light up at all. Please tell me the weak diff didnt give out! Need anymore info let me know!
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just did some reading up. Seems chevys have a problem with the thermal accuator. Its weird its like -11 here. Makes me wonder what temps these acutators are good for.
The colder it is, the longer they take to engage :shoot: stupid thermal units. If it isn't working at all, it is a good reason to get a posi-lok cable unit :bigthumb:
Yup! Sounds like the thermal actuator(peace of crap) i replaced mine when i had this problem. It lasted for about 3 months until i had to get another one. I didnt have enough money for the posi lock system, so i took it back to Advanced. Best thing to do is unplug the actuator at the front axle and see if you are getting a signal from the wire coming from the T case. If you are getting a signal, it should be the actuator that is broken. They run about 75 bucks and are very simple to install. Also check the 4WD fuse(should be next to the drivers door). Check your manual for that one. I replaced my actuator and the 4WD still didnt work until i replaced the fuse.
What would it be listed as at advance auto parts? Id checked the wires they were all good. I looked on the advanced auto website and didnt find anything. It would be easier to get one local to see if that is the problem.
Part No.

Try that first, but if that doesnt work just go onto the advanced page and type in the info on your truck and then look at the upper left corner and type in 4WD switch. then click on switches and 4 should pop up. there are two axle actuators and 2 t case switches as well. I have a 95 and im pretty sure its the same system as your truck.
well the main 4x4 actuator didnt do the trick. So i checked the diff drained it and no shavings. T Case works just dont lock in i guess.
hmmm. well, if the front drive shaft is spinning, the t case is doing its job. try shifting it into 4 lo. if the truck gets a lot of low end to the back axle, that will tell you if the t case is working. Did you start the truck and use a volt meter when checking the wires to the front axle actuator? IF you replaced the actuator and the font drive shaft spins, it could be a fuse, or the switch that is located on the t case. the switch is pluged into the back top of the t case. I havent heard of those swiches going out though. Good luck dude.
very important. when your actuator goes bad it usually blows the 4WD switch fuse. i believe its a 25 amp fuse located on the door panel of the drivers side. (In my manual it is fuse #24 and is labled (4WD) (Circuits protected are the frt axle, 4WD indicator lamp). Make sure to check that fuse!!!!!!!!!!!!hope this helps.
I have no checked the wires with a volt meter allthough I did check them with a test light. The transfer case is doing its job. I just cant get the halfshafts to even spin. Like I said i checked the diff oil for fragments and found nothing. Everything is turning except the halfshafts.
Fuse is good.

Changed the accuator.

Checked the bulb.

Drained the front diff checked for fragments.

Front driveshaft spins.

Halfshafts dont spin, but sping freely by hand.

Still no lite on the 4 lighting up.

Checked wires yp front both have juice.

Anyone have any Ideas.
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I have a 94 GMC Sierra and have also replaced the actuator twice. The first time noticed that 4x4 not engaging and the 4x4 light not turning on. Replaced actuator, took care of problem. Second time noticed 4x4 not engaging but sometimes the light WOULD turn on. Bought 4x4 posi-lok and it still did NOT work. Took to local 4x4 shop, they disassembled diff and found out that the gear that the actuator pushes to engage diff snapped in half. This gear is pretty thick and will not snap with light offroading. After thinking back, I remembered hitting a big rut going up a sandy hill and hearing something. Knew that it had to of been reason for gear breaking.

I also bought another actuator because 4x4 went out again (yes 3 times) and thought that the cable actuating posi-lok was not pushing gear far enough in to engage.

My suggestion: Pull out actuator, plug wires back, turn truck on and engage 4high. You can do that in park. If actuator acts like if he just saw Angelina Jolie in nothing but a thong :eyecrazy: , then something is going on inside diff.

Maybe new actuator you bought is not working.

Good luck and hope this helps.

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Now what the hell broke?
Bearing go out or what?
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