1. Vehicle History:
* Mileage: Lower mileage is generally better. A transmission with excessively high mileage is more likely to have internal wear. Check the odometer reading on the donor vehicle (if available).
* Reason for vehicle's demise: Ideally, the vehicle wasn't wrecked in a way that impacted the transmission (e.g., rear-end collision). Ask the junkyard staff about the cause of the vehicle's disposal; a wrecked car might hide transmission damage.
* Service records (if available): This is a long shot, but some junkyards might have minimal service records. Fluid changes are crucial for transmission longevity.
2. Visual Inspection (Crucial!):
* Fluid: Check the transmission fluid. This is the most important step. Look for the color and condition. Bright red, clean fluid is a good sign. Dark brown, black, burnt smelling fluid is a very bad sign, indicating severe wear and potential internal damage. A milky fluid suggests water contamination.
* Leaks: Look carefully for any signs of fluid leaks around the transmission case, bellhousing, or cooler lines. Even small leaks can be indicators of future problems.
* External Damage: Inspect the transmission case for dents, cracks, or other physical damage. Even minor damage can compromise its integrity.
* Wiring and Connectors: Ensure all wiring harnesses and connectors are intact and undamaged.
* Mounting Points: Check the mounting points on the transmission for any damage or signs of stress.
3. Junkyard Specifics:
* Reputation: Choose a reputable junkyard with a good return policy, in case the transmission proves faulty.
* Warranty: Some junkyards offer short warranties on their transmissions. This is a valuable safety net.
* Testing: Some junkyards may offer some form of testing (though this is rare), but visually inspecting the fluid is the best readily available test.
Important Considerations:
* No Guarantees: Even with careful inspection, there's always a risk when buying a used transmission. Internal damage might not be visible externally.
* Professional Installation: Have the transmission professionally installed by a qualified mechanic. Improper installation can void any warranty and damage the new-to-you transmission.
* Cost vs. Risk: Weigh the cost savings against the potential cost of a failed transmission and installation. A rebuilt transmission from a reputable remanufacturer might be a safer, albeit more expensive, option.
In short, a good used automatic transmission from a junkyard is a gamble. The best you can do is minimize the risk through thorough visual inspection and understanding the limitations of the process. The fluid condition is the most important factor to examine. If you're unsure, err on the side of caution and consider a professionally rebuilt unit.
