When I first saw this on my truck I also was like wtf, then I learned that there is a clutch type cplg on that shaft and engages completely when you engage the 4x4 or there is any force on the shaft. This is just for autotrac. you can actually turn the shaft by hand it is just a little hard to turn.

 

Neil, I don't think they made a 1500HD for '04. They skipped that year and introduced the 1500 CC and reintroduced the 1500HD for '05. So you may have been looking at a 1500CC? Check to make sure it has AutoTrac Auto 4X4 and not regular push button 4X4. Otherwise I cannot help explain those vehicles front driveshafts not turning when in gear with the engine running.

 

Are you 100% they are Autotrac? Just because they have pushbutton 4wd doesn't mean they have Autotrac. Maybe they have Instatrac, which only has the 3 buttons (2HI, 4HI, and 4LO)?

 

autotrack keeps enough tension on the front shaft so that it spins all the time but you can hold it back or force it to turn when in park. i think they desiged it that way so you could shift it into 4hi or auto while moving. if that shaft isn't moving you will need to stop before you shift into 4wd.

 

GM made the "1500HD" in '04, but they just re-badged the emblems on the door to 2500. Then they switched back to 1500HD badges in '05. (GM = ) I just called my friend's truck a 1500HD instead of a 2500 to try to avoid confusion from people who don't know the difference between a 2500 and a 2500HD.

And for everyone's viewing pleasure, this is the switch that is in all of the trucks I have talked about.

 

Neil, Could it be that the clutches are worn in the transfer case of those other vehicles?