What do i need to replace if have coolant in the transmission of my 02 ford focus?

Finding coolant in your transmission of a 2002 Ford Focus is a serious problem indicating a significant leak and likely internal damage. You almost certainly cannot just replace a single part and be done with it. The problem stems from a failure allowing coolant to mix with the transmission fluid. The most likely culprits are:

* Transmission Cooler: The transmission cooler is a radiator-like unit that cools the transmission fluid. It's often integrated into the main radiator. A leak in the cooler itself, or the lines connecting the cooler to the transmission, is the most common cause of coolant in the transmission. Replacing the cooler (or just the lines if that's the source) might seem like a solution but it's often only a temporary fix if there's already significant contamination.

* Radiator: A leak in the radiator itself, especially near the transmission cooler lines, could allow coolant to mix into the transmission fluid. This will likely require radiator replacement.

* Transmission Fluid Seals/Gaskets: Though less likely to be the primary cause of the coolant getting *into* the transmission, a severely damaged seal or gasket *within* the transmission could potentially allow contaminated fluid to leak *out*, further complicating the situation.

* Cracked Engine Block/Head: In extreme cases, a crack in the engine block or cylinder head near the transmission interface could allow coolant to enter the transmission. This is a very serious and expensive problem.

What you absolutely MUST do:

1. Stop driving the car immediately. Driving with a mixture of coolant and transmission fluid will severely damage the transmission, leading to complete failure.

2. Get a professional diagnosis. A mechanic needs to inspect the car thoroughly to pinpoint the leak's source. Simply replacing a part without knowing the root cause is a waste of money and could lead to further damage.

3. Prepare for potentially significant repair costs. Depending on the cause, repairs could range from relatively inexpensive (new cooler lines) to extremely expensive (new radiator, transmission repair or replacement, engine repair).

In short, you're looking at a significant repair job that requires professional expertise. Attempting a DIY fix without a proper diagnosis is strongly discouraged. The damage will likely worsen, and the cost will likely increase, the longer you delay professional help.