Is my Tach off that much or is it my Speedo?

[1992 2.3LX]

According to this calculator. http://www.wcfords.com/stuff/calcs/EGTcalc/egtcalc.php

at 65mph (5th gear) in a 96 with 2.73's and 245/45/17's I should be at
RPM = 1556. Well i tested this tonight and my Tach was clearly on 2000 @ 65mph.

So which one is more likely to be off and is there a way to remedy this?

 

[COramprat]

Hmmm...Possibly you have 3.27's. Check the door jamb at the production sticker and look at the code under axle or trans. If it is an "E" you have 3.27's. This is if the car is stock. Did you purchase it used? If so it could be you have 3.73's because that is what the calc shows at the speed and rpm's you provide.

 

[1992 2.3LX]

I thought all 96 5 Speeds came with 2.73's????

BUt I have an "E" on my door jamb.

well thanks for the info.