My vehicle shifts out of 4wd but the light on the dash will not shut off. I am sure that I am running in two wheel drive, and the light doesn't really bother me, but I want to make sure I am not damaging anything driving with the light on....as if something hasn't dissengaged fully and might be grinding or something like that.
Thanks

 

If you don't hear any rude noises, you aren't hurting anything, aside from your gas mileage, and even that, not very much.

The front axle is vacuum controlled, and notorious for being problematic. Check the lines at the central axle disconnect (CAD), there are two vacuum lines, the outboard side should have vacuum in 2wd, the inboard line should have vacuum in 4wd. If one side works, and one side doesn't, you prolly just have a broken vacuum line somewhere, if it doesn't switch at all, probably the switch on the t-case.

 

Thanks, two questions:

If I do have a broken vacuum line, that wouldn't effect the transfering into and out of 4wd? I can switch between them, just no change in the light.

Just out of curiosity, why would this broken vacuum line affect my gas milage?

Thanks

 

Most of the 4x4 is mechanical. The lever on your floor engages the front output in the transfer case. The light is controlled by the cad, light on means the passenger front axle is locked together, so, when in 4x4, power is transferred to the wheel with the LEAST traction, so, at least one of them will spin. (if you apply enough power.) When it is unlocked, doesn't matter what you do, the drivers side wheel won't receive any power, it will all go to spin the intermediate axle on the passenger side, as there is zero resistance to rotation there. With the front axle always locked, the only difference between 2 and 4 wheel drive is, whether or not the t-case is supplying power to the front axle. (and the front and rear are locked together.......) The T-case is supposed to control which side of the cad gets the vacuum, doesn't always work as it should.

By the front axle being locked all the time, you are spinning more 'stuff'.... namely, the front driveshaft. When things are working as they should, in 2wd, front driveshaft doesn't turn. So, you have the additional drag from trying to spin it, and that will affect your fuel economy. (but, probably not even by a full point.)

 

here's how everything works.
http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm


for the light problem, look on the end of the cad, drivers side, and see the electrical plug. when these 2 wires are shorted together, it will turn the light on. the light should go out when you unplug this connector. check for damage, clean out the mud, spray out both sides of the connector with wd40. on the end of the cad is a contact switch which can also be removed, checked, and/or replaced. its available at all parts stores for about $20 or less. if its acting up you might can clean it inside.