I felt something in my transmission go pop a week ago. The dealer found gears missing a tooth or 2, they have decided to replace the transmission instead of just the damaged gears. In warranty. So my question. Is Synthetic better in a manual transmission? And if so, Do I offer to pay for synthetic transmission fluid? Side note: more info on same issue. After I felt the transmission go pop into 5th gear it just did not feel right. Sliding it into gear was not as smooth, and when I got up to high speeds it would sometimes grind going into 5th. I found I could produce the grinding issue 100% of the time if I did this: 6mph+, shift to neutral, let the clutch out, push clutch back in, shift to 5th gear. So now basically what they are telling me: “You should not double clutch a car with synchro’s, it could cause damage. Double clutching should only be done in large trucks without synchro’s” That sound like a bunch of bull shift to you also? I have driven a stick on and off for 30 years, from a VW Bug to large truck. I am shifting as I always have – sometimes leaving the transmission in neutral. This is the 1st transmission I have ever had any problems with. I do NOT see how double clutching can cause any issue. IMO it helps. If anyone can point me to any verifiable documentation on the issue of double clutching in a car with syncros PLEASE let me know. I would love to hand them verifiable documentation.