A heavy-duty truck equipped with a manual transmission experiences consistent difficulty engaging reverse gear when the engine is running, but reverse engages smoothly when the engine is off. All other gears engage without issue. What is the most likely cause of this problem?

Question: A heavy-duty truck equipped with a manual transmission experiences consistent difficulty engaging reverse gear when the engine is running, but reverse engages smoothly when the engine is off. All other gears engage without issue. What is the most likely cause of this problem?

Answer options:

• Worn reverse idler gear or fork ✅ Insufficient clutch free play or a dragging clutch
• Damaged synchronizer for reverse gear
• Low transmission fluid level

Correct answer: Insufficient clutch free play or a dragging clutch

Explanation: Difficulty engaging reverse with the engine running, but not when it's off, strongly indicates a dragging clutch that prevents the input shaft from stopping completely. If the reverse idler gear or fork were worn, it would likely be difficult to engage reverse even with the engine off. Reverse gears typically do not have synchronizers, so a damaged synchronizer is not the issue. While low fluid can cause shifting issues, it wouldn't selectively affect only reverse when the engine is running in this specific manner.