I have a 1995 Honda Civic 5 speed. It has 125K miles. I had a tune up last month. Since then there has been a loud noise when the car is idling (not in gear); but a quieter sound when the car is in gear. I took it back to the garage to ask what the cause was and why it was not picked up during the tune up. The answer was that the tune up focuses on spark plugs, timing belt, caps etc...). The garage reports that this sound is coming from inside the transmission. It could be a worn out bearing. The recommended fix is replacing the transmission. A used transmission will cost $850 installed, a new one will cost $1,350 installed. Does anyone have a view if this is the correct diagnosis and if so, which fix makes more sense?