You removed the sound deadning . Well that should answer your question . My manual 300D is a little whiney in second but nothing aggravating and because it only has 131,000 on it ,I'm not about to mess with it. Stick to the regular ATF ,Mercs have used it since the 50's in all their cars with manual trans without a problem and changing up to an expensive synthetic won't do anything to make the trans quiet. But if you replaced the sound deadning material....