my trans dont shift on overdrive
I am sorry to hear you Model T Ford is having a problem… 
We need more information. Make model and year of car (assuming it is a car) along with the current mileage and any repairs or maintenance it may have received. Has the transmission fluid ever been changed? How long has it had the problem. How long have you owned it? Is there anything else going on with the car? Do you have a CEL Check Engine Light on?