A couple things to check:
1) After you have verified the deck does not appear to have any drag in it, take the tractor some place where you can climb hills, but no grass to cut. Set the deck high. Drive the tractor up the hills. We're trying to put the tractor drive under a load, but not add the cutting of grass to see where your power is...... or is not.
2) On a flat driveway, check the settings of your deck to the ground. If the front is higher than the rear, the blades cut the grass 2 times, once in the front of the deck, and again at the rear, where, if it is absolutely flat, or the front tipped down just a bit, you only cut the grass once.
1) After you have verified the deck does not appear to have any drag in it, take the tractor some place where you can climb hills, but no grass to cut. Set the deck high. Drive the tractor up the hills. We're trying to put the tractor drive under a load, but not add the cutting of grass to see where your power is...... or is not.
2) On a flat driveway, check the settings of your deck to the ground. If the front is higher than the rear, the blades cut the grass 2 times, once in the front of the deck, and again at the rear, where, if it is absolutely flat, or the front tipped down just a bit, you only cut the grass once.