1. As previously suggested, definitely read the OM cover to cover at least a couple of times.
2. “Front wheel drive” isn’t front wheel drive as defined on a front wheel drive car. The rear wheels ALWAYS drive. Whether the front wheels are engaged or not is selectable. Same as a 4WD pickup.
At least in some areas these type selectable 4WD tractors are referred to as “front wheel drive” or “front wheel assist” to differentiate them from articulated tractors with same size wheels front and back which all drive all the time which are called “four wheel drive”. That difference in semantics from the road vehicle world to tractor world can be a bit misleading.
Some of the reasons for 2WD v 4WD for a tractor are same as they are for a truck or Jeep. 2WD: pavement, not tearing up grass when turning, high speed driving. 4WD: maximum traction needed for soft ground, steep terrain, etc.
Some additional considerations for engaging front wheels on a tractor.
1. The tractor has rear brakes but no front brakes. If you’re going downhill with a load in the loader, front brakes are somewhere between helpful and necessary. Having it in 4WD ties the front and back wheels together so when you brake the back wheels, that braking force is transmitted through the transmission to the front wheels, effectively giving you front brakes. So if you’re going downhill with a load in the bucket 4WD is a good thing.
2. Any time you have a heavy load in the loader, it decreases rear wheel traction. It can be difficult backing up even a slight incline in 2WD.
Using grapple or bucket, mine is in 4WD about 99% of the time. Mowing relatively flat areas or roading it; 2WD. Mowing steep rough areas, skidding logs, anything requiring heavy pulling; 4WD.