Watch for leaks or stains under the car
If there is a persistent red oil leak that you are sure is coming from your car, you should have your shop check to see if it is coming from your transmission or possibly from your power steering system (most power steering systems also use transmission fluid and leaks can appear on the ground in roughly the same areas as transmission leaks.) If all you see is a few drops on the ground, you may be able to postpone repairs as long as you check your fluid level often (but check with your technician to be sure.) If transmission fluid levels go down below minimum levels serious transmission damage can occur (the same advice goes for power steering leaks as well.)
Check fluid for color and odor
Most manufacturers require that you check transmission fluid levels when the vehicle is running and on level ground. Pull the transmission dipstick out and check the fluid for color and odor. Transmission fluid is a transparent red oil that looks something like cherry cough syrup. If the fluid is cloudy or muddy, or it has a burned odor, you should have it checked by your technician who will most likely advise you to have a transmission drain and refill or transmission tune-up. See the Maintenance section below for details on this service.
Be sensitive to new noises, vibrations and shift behavior
A modern transmission should shift smoothly and quietly under light acceleration. Heavier acceleration should produce firmer shifts at higher speeds. If shift points are erratic or you hear noises when shifting, you should have it checked out immediately. Whining noises coming from the floorboard are also a cause for concern. If caught early, many problems can be resolved without costly transmission overhauls. Even if you feel that you can’t afford repairs at this time, you should at least have it checked. The technician may be able to give you some hints on what to do and not do to prolong the transmission life until you can afford the repair.