If your loader is slow to you might have lost pressure some where. I'd check the hydraulic filter it's on the left hand side of the tractor under the floor right in front of the rear axle and cut it open to see if there any metal flakes in it or brake material where a brake came apart. Like outback said there's a screen you can pull out its on the rear axle housing I can't remember if it's under the PTO on the 6000 series tractor or under the axle housing or in front of the rear axle housing just below the hydraulic filter on the right hand side. If all those check out ok you need to get you a service manual and a oil pressure gauge to start checking ports for hydraulic pressure. It could be as simple as a blown o ring or pump failure those tractors have a pump in the belly of the tractor and a pump at the front of the engine driven off the crank. Just hope and pray you don't find a lot of brake material like the brake disc material let go.