I got a question for you guys . I buy a cavy last week and I want to change my transmission oil ... but I don't no how many quarts to put in . My transmission is a 3 speed auto (3t40E ... i think ) . Thank you guys and sorry for my poor english

You have a 3 speed automatic so you should have a dipstick to check the level. Best to check the level with the tranny hot. You will have to add until you get to the top level on the dipstick hot... Go buy 6 quarts of tranny fluid for your GM product and that may be enough to get the job done. Not sure of the exact capacity you will be dealing with.