If you have a FEL, use it to lift the front tires and then disengage MFWD. If you don't have a FEL, jack up the front of the tractor and take it out of MFWD. If you have a well-lubed lever and pivot points, you can engage and disengage MFWD by moving slowly forward and reverse while rotating the steering wheel from side to side. No matter what tires you have, the front axle will "wind up" the driveline and keep it under tension. The trick to engaging and disengaging MFWD is to relieve the tension.