Lincoln/Mercury Repair: Mercury Sable 1991, mercury sable, foot on the gas

Question
I have a mercury sable 91, and for the past two days it has been jerking when I come to a stop (at a red light)and let my foot off the brake. It jerks in the time between letting my foot of the brake and putting my foot on the gas. It also has been jerking when my car is in reverse. I took it to the mechanic today and they said that it was the tranmission. I was just writing to see if it could be anything else?? If it isn't would it be worth it for me to put money into this car?? Thank you for any help you may be able to give me  

Answer
hello farah
tell them to check the timeing belt this will make it do the same thing . make sure they are right .
a 1991 would not be worth it to change the tranny 1800 to 2000 to do a tranny job . good luck to u hun and if u need more help let me know u have a pretty name please rate my serivice pete