I am embarrassed to even ask this question but am at a loss on how my drive-line should work.  I have a 1988 DL 4wd wagon.  When not in 4wd my drive-line still rotates.  Should it?  I thought that when I pushed the orange 4wd button on the shifter that the drive-line would begin rotating thus engaging the rear wheels.  Should I expect the drive-line to stop spinning when I am in normal 2wd?  Am I wrong? 

Are you checking the drive line while the car is raised or rolling across the ground?

 

When in 2wd, I imagine the drive shaft is disengaged from the transmission but is still connected to the rear wheels. If the car is moving, the rear wheels will turn the shaft freely. But when you enable the 4wd, the drive shaft will engage and the transmission will be turning the wheels.

Edited April 25, 201312 yr by Coyote Paws

Subarus don't have actuating hubs or diff the whole action takes place in the trans, but the rear wheels shouldn't get power when out of 4wd. Just see if you can spin your front tire without the backs moving, get in some wet grass or loose gravel and romp on the throttle

Whenever the rear wheels are turning, the driveline will be turning.

 

In 2wd it just rolls behind the car, not driven by the engine.

 

Same would be true the front driveline on 4wd truck, if you didn't unlock the hubs.  Subaru does not have locking/unlocking hubs so the driveline is hooked to the rear wheels all the time.

Two of the responses sort make sense but ultimately if my shaft rotates that means my rear wheels are rotating and engaged.  The crux of the issue is whether my car is front-wheel drive or rear-wheel drive when in 2wd; not 4wd.  I have always thought that my car was front-wheel drive in 2wd.  Reading the responses it appears likely that my car is actually rear-wheel drive in 2wd, then pushing the orange button and the front wheels engage via the transaxle.  Having it the other way around does not make sense; however as per the first response, stomping on the accelerator in loose gravel makes my front tires spin when in 2wd.  It is still confusing.   I have only one set of jack stands so I will have to borrow another set of stands and go from there.

In 2wd the rear driveline is turning, but it is not coupled to the front driveline and recieves no power in 2wd.

 

It's just turning because the car is rolling along.  It is disconnected from the engine inside the rear of the trans.  When you shift into 4wd, the Front and rear get coupled toghether and both recieve power.

 

Do you get it? it turns ONLY because the car is rolling.  The car is FWD in 2wd. 

Fwd in 2wd, rear wheels only get power in 4wd. Driveshaft will rotate with the wheels as the car moves since it has soild hubs/diff.