Ratchets have a square shaft that holds the socket. The size of this shaft determines the drive size. Heavy-duty automotive work generally requires the strength of a 1/2-in. drive tool which has a longer, thicker handle to provide maximum leverage. A 3/8-in. ratchet is a good all-round size. 1/4-in. ratchets are smaller and ideal for lighter tasks in tighter work areas. Drive adaptors are available that convert sockets from one drive size to another. You should avoid using a small socket on a 1/2-in. drive ratchet, because the excess torque can damage the smaller tool.
By sending in extra money each month or making an extra payment at the end of the year, you can accelerate the process of paying off the loan. When you send extra money, be sure to indicate that the excess payment is to be applied to the principal. Most lenders allow loan prepayment, though you may have to pay a prepayment penalty to do so. Ask your lender for details.