when in normal driving, shifting at 3k rpm my speed seems to be 5 to 10 mph off. in third gear at around 2.5k rpm, if i punch it to redline, ill top out at like 65-70 mph. in 4th gear on the highway at 3k rpm im doing 65. when i shift to 5th my rpm drops to 2.5k doesnt seem right to me.

any ideas?

my first honda. ive got a stock d16z6 with i believe a stock ecu.

 

Speeds and RPM are meaningless without knowing what car/transmission you're talking about, along with the tire size. That said there's nothing wrong with the speed sensor. They either work or they don't, or they work intermittently.