I run 2.78 in my cars and get 2500rpm at 100km/h. Dad has 3.36 and gets 3000rpm at 100km/h. (all approx.). These are with approx standard diameter tyres. With 3.55 you'd be getting 3200rpm at 100km/h and 3.08 2750rpm at 100 km/h.


The Laycock overdrive is 0.78 so 78% of the above revs depending on which rear axle you have.