Toyota Repair: 1988 Corolla Automatic Transmission, metal particles, salvage yards

Question
Recently since it has been cold outside my transmission has started slipping only when it kicks into overdrive at highway speeds. It sometimes shifts a little hard moving up through the gears, but never slips. It only has 135,000 miles on it, and I was hoping maybe there was a way to fix overdrive without having to get a whole new transmission. Also, if overdrive goes out, will it mess up all of the other gears?

Answer
Transmission parts are extremely expensive, we do not try to repair them because of high cost of parts plus the labor cost, it could easily cost $2000 to repair the transmission, normally when there is a problem metal particles from the failing part will contaminate the transmission fluid and get into every part of the transmission.
It's best to just replace it with either a remanufactured unit, make sure it comes with the torque, converter or a good used unit. There are salvage yards that specialize in used engines and transmissions, try to locate one near you.
Most toyota dealers will help in locating a used transmission and install it for you.