Secure a personal loan through your bank or credit union. If your car is fully paid off, offer the car as collateral so you can borrow from the bank for a new transmission.
Negotiate with independently owned auto shops and ask the shop for a payment plan. The managers at these shops have more decision-making authority than managers at large national chains. Offer upfront to pay interest. Give the shop some kind of collateral, such as a signed agreement deeding your car to the shop if your loan isn't repaid within the specified time.
Apply for a credit card. Search for one with a low introductory interest rate. These rates, also known as teaser rates, are low for a limited period before spiking dramatically. This is a good option if you repay the loan while the teaser rate is still in force.
Apply for a loan on a person-to-person loan website such as Prosper.com, where a stranger will review your credit score, finances and the reason you need a loan. If the stranger likes your profile, he'll offer you a loan at a mutually agreed upon interest rate. State the loan is needed for a transmission, so lenders feel more secure in lending money, since you're not using it on a more risky venture, such as starting a business.