my transmission "clunks" when it shifts and the engine speed is low. This usually happens after shifting into second, I reach the speed I want and let up on the gas and the car "clunks" into 3rd. However, it'll happen in any gear if the car is not really accelerating and it decides to shift.

I am far from knowledgeable about transmissions, but I figure that this sound is not a good think. I have been modifying my driving patterns to avoid clunking until I can do something about this.

Do any of you know what might be going on? If I avoid the clunking am I helping things to not deteriorate as quickly?