Originally Posted by
03-Galant-ES
I agree with you there. I would check the trans that seems like the most likely issue. Trannies dont have to make noise if they are shot.
You said it shifts smooth so it doesnt seem like clutch, but 5th gear may be shot on the tranny. This is not a cat problem and it doesnt sound like a fuel problem. Trans is best bet Alex. Just stay under 100 until you can find some way to test another tranny in the car or have the tranny diagnosed by a shop.
Maybe try doing a 5th gear pull from 1k rpm. I know this is a bit of a strain, but it will be the best way to see if 5th gear slips at all. If that doesnt prove anything it still doesnt mean 5th gear isnt shot.