well, yesterday me and my friends installed the dual invidia exhaust system on my car and ever since, i've been grinding in 5th gear. i'll go on the freeway, and whenever i try to shift into 5th gear, i grind. it won't even let me put it into 5th gear. i put it in neutral then i can put it into 5th gear. i'm not an inexperienced manual driver, however i do not know enough about engines and transmissions to know why my car keeps grinding in 5th gear. can anyone help?

 

You might want to take a look at this post in the technical section. It shows a possible cause of the infamous 5th gear grind

https://www.s2ki.com/forums/index.php?showtopic=237209

 

I can't see offhand, any direct correlation between putting on a cat back exhaust and then suddenly getting a 5th gear grind. I know that whenever I put something new on the car that might affect performance, I go out and really let 'er rip. In doing so, the added exuberance may be what is causing this grind to start. Once you start to grind, the more you will continue to grind.

 

the exhaust *could* be causing a faster drop in revs between shifts, which could therefore change your shift timing. i don't think this would cause a grind, but it could be a part of it. 5th is the hardest gear for me to hit quickly.