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Discussion Starter #1
I just bought a 98 dodge ram.

I read a lot on this. Might go to posi-lok, but want to try this first.

When driving my 4wd light will come on and stay on till i come to a stop.
I can't turn my front axle when parked. When i do the truck goes either forward or backward.

When i put it into 4wd it goes into it just fine and when i take it out it goes off. But that light comes back on when i start driving again.

Any ideas. I have checked my vac lines, one had a hole in it so i replaced. I took out and cleaned the indicator lamp switch, and also the switch going into the trany with the 4 vac lines coming out of it.

Should I replace one of them switches?
 

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Woodstock
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If you haven't installed a locker in the front diff, when in two wheel drive you should be able to turn the front drive shaft by hand. If it doesn't turn the CAD is staying engaged. If it's staying engaged then either you still have a vacuum problem or the CAD is bad.
The 4wd light should only be on when the CAD is engaged.
 

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Woodstock
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No. Not if the transfercase is in 2wd. You will just have less gas mileage. If you drive with the axle engaged for a long period of time you will get unneeded wear on the front drivetrain components. All of the old full-time 4wd trucks did not have the CAD and were driven forever.
 

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Discussion Starter #6
LOL i have had a 4wd truck before this one for 4 years. Thanks though. I am going to fix it this weekend to get the front dissengaged. What kind of oil goes in the front axle is it 80-90?
 

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Woodstock
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Yes.
 

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I have the same problem with my 4wd light flashing on and off and there is also vibration along with it, not sure where it is coming from. Some people have told me it could be the CAD or the bushing inside the CAD could be shot, any help would be great.
 

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Discussion Starter #9
actually my metal vacume hose got a hole in it from rubbing on the cat... I replaced the whole hose and it works now ..
 

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Woodstock
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actually my metal vacume hose got a hole in it from rubbing on the cat... I replaced the whole hose and it works now ..
Great to hear you got it fixed. :SPIN:
 

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Woodstock
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Did you have a vibration problem or just the light coming on? Cause I am having both all of sudden at the same time.
Sounds like your front axle is engaged. Vibration could be coming from a bad u-joint in the front drive shaft. If the CAD is staying engaged the front drive shaft will turn all the time you are moving. (front drive shaft should not turn in 2WD)
The switch is located on the end of the CAD and should only be on when the shift fork inside is in the engaged position. To check if the CAD is engaged in 2WD you can start the truck and try to rotate the front drive shaft. With the transfer case in 2WD the shaft should turn by hand with both front wheels on the ground.
 

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Woodstock
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Central Axle Disconnect. Sometimes called a Vacuum Shift Motor. When someone says CAD they are usually referring to the vacuum shift motor, disconnect housing, and the shift fork.
 

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