Here the Sign for the Transmission Problems:

Problems occurring when a transmission is trying to make a gear change.

A noise associated with the problem or just general noises from the transmission.

Problems occurring when you first put the transmission in gear.

Problems occurring when the vehicle is hot or cold.

Problems occurring when accelerating, or stopping.

Diagnosing

Check if you have sufficient transmission fluid. Different vehicles have different ways to access the transmission fluid level, the general rule is you measure the fluid with the transmission in park. If you see you do not have sufficient fluid, fill the transmission to the proper level. Test drive the vehicle, if you no longer feel the problem, wait a day and recheck the fluid and underneath the vehicle. If it is low, the most likely problem is a fluid-leak. A leak, no matter how small, must be checked by a technician.

If you find that your transmission is not leaking, but a problem persists, take your vehicle to a technician. The problem may be so minor that you may not even be charged. However, a qualified technician may be able to diagnose a major problem before it occurs and recommend minor service.

Avoid Transmission Problems:

Vehicles which are driven occasionally subjected to unusual wear and strain. Consistently never have the opportunity for the engine to warm up to the normal heat range. This can cause excessive engine wear.

Relatively, low mileage transmissions which are regularly used in city or stop and go conditions are subject to much higher wear than transmissions of the same mileage which are used under normal or primarily highway conditions. It is important to note that that it is not necessarily the mileage on a transmission which determines probable wear. Rather, it is the number of times the transmission has been run through its start-up and shift cycles that determines probable wear.

Many other seemingly normal driving conditions can affect transmission life. Things like extreme climate conditions either cold or hot, mountainous, driving, motoring problems which are associated with snow or ice can take their toll.

Under 'normal' driving conditions vehicle manufacturers recommend servicing your transmission as seldom as every 10,000 miles or once per year. As you can see from the limited examples above, very few motorist fit into the ideal or 'normal' driving condition category.

If you operate your vehicle under more extreme conditions, more frequent transmission servicing will be necessary to maximize transmission life. Servicing your transmission yearly seems to be an industry average. Under the most extreme conditions, even more often may be advisable and you may want to install an external transmission cooler for additional protection.