My friend that has a 96 HX manual recently got her tranny and her alternator replaced. She's not very car savvy, but she does know that her car shouldn't be running at 4k @ 80mph. She told the mechanic that worked on the car about the situation and he said that this is normal.

My question is, what would cause this? My best guess was that even though she got a civic tranny, she got one that wasn't meant for her car (for the HX trim model anyways). Any help would be greatly appreciated. Thanks.