* Transmission Cooler Failure: Many automatic transmissions in that era use a transmission fluid cooler integrated into the radiator. If the engine overheated severely, the radiator could have failed (leaks, cracked) or become significantly less efficient. This would prevent proper cooling of the transmission fluid, leading to overheating and boiling. A clogged cooler is another possibility, even without a radiator failure.
* Low Transmission Fluid: If the transmission was already low on fluid, overheating would exacerbate the problem, making the fluid thinner and more likely to boil. Low fluid also increases friction and heat generation within the transmission itself.
* Internal Transmission Problems: A failing transmission (worn clutches, broken internal parts) generates excessive heat. An already stressed transmission is much more susceptible to boiling over during an engine overheating event. The engine overheating might have simply revealed a pre-existing condition.
* Radiator Hose Failure (Rare): A highly unlikely scenario but possible; a failed hose connecting the transmission cooler to the radiator could cause a sudden loss of coolant or a mix-up between transmission and engine coolant.
* Incorrect Fluid: Using the wrong type of transmission fluid can reduce its heat tolerance, making it more prone to boiling.
In short: The engine overheating likely didn't directly boil the transmission fluid. Instead, it severely stressed the cooling system, likely damaging or compromising the transmission cooler, or revealed an existing problem within the transmission itself that lead to overheating of the transmission fluid.
What to do:
1. Check the transmission fluid level: This is crucial. Is it low? Is it burnt or discolored?
2. Inspect the radiator and transmission cooler: Look for leaks, damage, or blockages. A mechanic can perform a pressure test on the cooling system.
3. Check the transmission cooler lines: Inspect for leaks, kinks, or clogs.
4. Have the transmission inspected by a professional: This is important to determine the extent of any internal transmission damage. A simple visual inspection won't be enough.
Ignoring the problem could lead to significant transmission damage requiring a costly rebuild or replacement. Get it checked out as soon as possible.
