One of the things we sometimes see in our transmission shop is clients requesting for us to install used transmissions in lieu of having us overhaul their failed transmission. This always comes down to budget, as a used transmission is almost always cheaper. This can be a very bad idea though. Simply think of it this way: Why would you want to install a used transmission, when you already have one?
The main issue with installing a used transmission instead of overhauling one is the condition and expected service life of the units. An overhauled transmission has zero miles on it, updated parts, and a generous nationwide warranty on both parts and labor. When we overhaul a transmission you know exactly what you’re getting: a guaranteed high performing unit. A used unit? Not so much.
Where does a used transmission come from? They are generally salvaged from unserviceable vehicles at junk yards. If a vehicle is wrecked in a crash that completely destroys the engine, but the transmission appears intact, scrap yards will simply remove the transmission and sell it with little to no knowledge of its performance. Herein lies the problem, as you cannot test a transmission outside of a vehicle, and inspecting the interior of the transmission would practically require an overhaul.
These transmission units will also come with questionable warranties depending on their source, such as only warrantying the unit and not the labor, or having very small warranty coverage miles and time windows. Why would you replace a transmission with a unit that already has 80,000 miles on it without even confirming its mechanical condition?
Sometimes clients are simply not in a financial position to buy an overhaul, but if you’re thinking about a used transmission with the ability to purchase an overhaul, we advise you to get an overhaul and save yourself a possible headache down the line.