2000 4x4 Blazer front end moan/noise

[billkater]

I purchased a 2000 Blazer 4x4 (S-10) last year just before winter. I wanted my girl to have 4 wheel drive for her first year of driving. I just recently was doing some work on it (brakes and a new catalytic converter). When test driving it I hear a moan or a hum in the front end like the 4-wheel drive is engaged. You only hear it when the truck is moving so I know it is in the drive train.

I jacked up all 4 wheels and put it in drive. The front wheels do not turn and the drive shaft leading to the front end does not turn when in 2 wheel drive. I push the 4x4 high (or low) button and the front tires kick in and turn like they should. I push the 2x4 button and the front tires stop turning but the noise is still there.

While all 4 tires are still jacked up I turn the front tires (either side, it doesn't matter) and the front drive shaft leading to the transfer case turns.

So, here are my questions:

1. should the front drive shaft turn while spinning the front wheels in 2 wheel drive?

2. Is there a clutch of some kind in the front end to engage the front end and lock it into 4 wheel drive?

3. If so, could this be stuck or not being told to disengage and be causing the noise/problem?

Thanks for you help in advanced.

Bill

[MT-2500]

Jacked up in 2W you should be able to spin each wheel without turnine the drive shaft and turn the drive shaft without turning either wheel.

In 4 wheel the front axel on left side locks the axels and wheels and front rear end toghether and also locks them to the driveshaft.

The transfer case locks the front drive shaft into the transfer case gears.
Depending on what transfer case you have the front drive shaft will klock solid with the rear drive shaft or will engage auto as needed with the auto transfer case.

Now on the moan can you hear it when jacked uo in 2W or 4W.

On the road does the moan change with the engine RPM or the vechical MPH?

When going straight down the road from 30 -45 MPH turn the steering wheel a little left or right and see if the noise changes or gets louder or goes away.
Post back what you find.
MT