A If the 4WD lever is difficult to shift to '2WD', stop the vehicle, turn the steering wheel in both directions and then move the lever. A Tires will wear quickly if front wheel drive is engaged on paved roads. Shift the lever to '4WD' to engage the front wheel drive. Use the lever to engage the front wheels with the vehicle stopped. I hope you find this information helpful and it's a pleasure to help anyway I can. If this is difficult or not successful, it's an indicator that you have internal problems and you may want to drain the oil to see if you have any signs of metal or debris within the oil that would flag a mechanical failure requiring disassembly for further inspection for repair or rebuild.if this is not something you are comfortable with and do not have the appropriate shop manual, I recommend at this point that it should go into the shop for proper repair.
Once confirmed, you can then check to see if you can manually engage or disengage four-wheel drive at your transmission or transaxle assembly. Disconnect it from the opposite end to then confirm that you can move the lever freely confirming that there is no problems with the cable or your lever.
Take a very close look at the control lever for your four-wheel drive and the cable to see if it is binding or if there is any damage or problems with the control lever and cable.
