1998 Chevy Suburban 4wd problem

Hello there,
I am a new owner of a beautiful 1998 Suburban, have a problem and need help - as there aren't any Chevy dealers here in Slovakia :D

The car runs without any Problems as long as in 2wd mode. No noise, no nothing, just enjoying the ride... The switching into 4hi or 4lo as itself also runs without any problems, blinks 3 or 4 times and it is engaged. The real problem is, when I try to move the car from a stopped
position. The front axle acts like I would have my parking brake on, the car needs power to become moving, after it reaches about 10 km/h everyhing is fine and the car is driveable without any problems. During
the acceleration until 10 km/h the front and rear wheels somehow slip for 1 or 2 seconds. All of this is mostly noticeable when steering to the left or right from a stopped position. When switching to 4auto and starting from a stopped position, the car sometimes nearly "jumps" does
a very fast movement to the front and stops afterwards when trying to accelerate.
Can anybody tell me where to look and what might be the problem ? I am very helpfull for ANY hints as there is NONE Chevrolet dealer or service in the whole country :-)
Thank you.
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