TT is a "Torsion Twist". It basically means adjusting the tension of the torsion bars to adjust ride height up front. This is accomplished by loosening or tightening the adjustment bolts located in the crossmember where the torsion bars end. As far as special equipment, all that is required is longer U bolts and lowering blocks for the rear, and camber adjustment plates for the front. You can get generic kits online, or at the auto parts store, but you'll probably have to re-bend the new U bolts to fit around the Explorer's larger axle. Or you can buy the Explorer Express X-Spec kit which has the correct U-bolts and camber plates included. You will have to go to an alignment shop to have the plates installed, and get the wheels re-aligned, but the blocks, U bolts and torsion bar adjustment can be done at home if you're comfortable doing it, and have the proper tools.
Depending on the kit, and labor costs, it can run you around $200. This is a very broad ballpark number as it depends on the kit you buy, and how much you have the shop do.
When I did it, I bought the X-Spec kit (3 inch blocks and camber plates), installed the blocks and U bolts myself, and took the torsion bolts all the way out to let it settle as far as it would go, then took it to a shop to get the plates installed, and get it aligned. So for me, about $150 for the kit, and 50 for the labor.
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