A powershift transmission in a mining shovel is operating at excessive temperatures, causing the machine to occasionally de-rate. The transmission fluid level is correct, and there are no external leaks. What is a common cause for elevated transmission fluid temperatures?

Question: A powershift transmission in a mining shovel is operating at excessive temperatures, causing the machine to occasionally de-rate. The transmission fluid level is correct, and there are no external leaks. What is a common cause for elevated transmission fluid temperatures?

Answer options:

• A faulty transmission speed sensor
• A restricted transmission oil cooler or lines ✅ Worn internal friction discs causing excessive slippage
• Clogged transmission breathers

Correct answer: Worn internal friction discs causing excessive slippage

Explanation: Worn internal friction discs (clutches) or excessive converter slippage generate a significant amount of heat within the transmission due to friction, directly leading to elevated fluid temperatures. A restricted oil cooler would also cause overheating, but worn friction discs are a direct internal cause of heat generation. Speed sensors or clogged breathers are less likely to be direct causes of widespread excessive heat.