Drain the oil from the transfer case ("Changing the oil in the Niva Chevrolet transfer case").
Disconnect the corresponding cardan shaft from the transfer case, article - "Removing the cardan shaft"
Removing the intermediate shaft in the article - "Replacing and repairing the intermediate shaft"
Unscrew the flange nut, having previously locked the differential of the transfer case and turned on transmission.
Remove the nut and washer.
Remove from the shaft flange
Remove the seal with a screwdriver
Apply sealant to the seating surface of the socket in the crankcase under the seal, lubricate the working edge of the seal with oil and press the seal with a suitable mandrel.
Install the removed parts in the reverse order