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i have a 02 4.6..4WD was working perfect untill i shifted in today...dash light indicated that i was in 4X4 but i was slipping all over the road and soon realized 4X4 was not working..dosen't work in high or low..any suggestions on what might be causing this problem ?...thanks.

TheJMC

One of 2 things; Front axle not locking up or faulty t-case or shift mechanism. Which system do you have? Manual or electronic?

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manual...

TheJMC

If it is a manual shift the odds are that it is the front axle that is not engaging. Lift and support the truck so the front wheels are off the ground. Shift into 4H and try to turn the front axle. It should not turn. If it does than the t-case has an internal problem. If it does not turn start the engine with the transmission in Park or Neutral, to provide vacuum for the front axle engagement, then rotate any one of the front wheels. The other wheel should rotate in the opposite direction. If it doesn't the front axle is not locking. Please advise your results as I need that to know what further diagnostic procedures to post.

Regards

Jean Marc Chartier

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thanks alot...i will see if i can get out in this snow and try that...i will post as soon as i try it....thanks again.

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it seems like im not getting any vaccum to the front axle...its not locking in...

TheJMC

There are two vacuum solenoids on the firewall behind the battery. They control the vacuum going to the shift motor on the front axle. They have a constant 12volts going to them, red wire, and the GEM grounds them to control axle lock up. I'll dig up the schematics for the fuse number and the wire colors and post back.

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hey, i tested the plugs-ins and i have power so i switshed the vaccum hoses on the solenoids and she engaged 4x4..so i assume that one of the solenoids is not working...is that right ?

TheJMC

Not necessarily. If the GEM doesn't ground the solenoid it will not operate. Was your truck in 4H when you switched the vacuum lines?

Regards

Jean Marc Chartier

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hey i picked up two used solenoids at the scrap yard for $45 and tried those...everything works perfect now...thanks for the help...appreciate it very much...