I have a 2003 base pontiac vibe 5-speed, with the 1.8L. I use mobil 1 5w 30 full synthetic, i decided to change the manual trans fluid. After some research online, i decided to go with Red Line 75w90NS synthetic gear oil. This car is driven extremely gently, but when i am at 15mph, engage clutch into first, while clutch is completely engaged something grinds loudly, downshifting into first is the only time it grinds. Once the gear is engaged no more grinding..... So meanwhile i have switched to mobil 1 synthetic
75w90... still having the problem.. have about 11k miles, any thoughts on what the problem could be is appreciated.. Also, changing the trans fluid yourself dosent void the warranty does it? Is this something that is not covered by the initial 36k warr? thanks for your time.