This stands for Original Equipment from Manufacturer. What this means is that the replacement part is made by the same manufacturer as the original part that needs to be replaced. An OEM part is perfectly engineered to work with your car or truck’s transmission. Generally speaking, this is what you want.
The other grade of parts is called aftermarket parts. An aftermarket part is any part that is not sourced from your vehicle’s manufacturer. This doesn’t necessarily mean that it’s a substandard part. Many aftermarket parts are high performance parts that are better than the original. These parts are used when a car is being souped-up—such as a hot-rod. When this is the case, the aftermarket part is almost always more expensive than the original part.
The problem with aftermarket parts that comes into play is that when a repair uses aftermarket parts that are cheaper the original parts to save money. This is a situation where you get what you pay for. Cheap aftermarket parts are usually low-grade and poor quality. And you can expect below average performance from them. They can also shorten the life of your new transmission. Don’t let this happen to you. Always make to ask about OEM parts.
You always want to make sure that you know if the repair shop will be order OEM parts for your transmission.