LSX rear gear question

[Clyde65]

I have the 4.8/4l60e in my truck, was told I had 3.08 gears in my 12bolt truck 3series rear end.

I put a tack in the truck recently and when Im driving down the highway at 70, it shows 2250rpm, which, if you use one of those rear gear calculators show I have a 3.73, am I reading this right or is the tune wrong because I have 27.1" tires ( 255/60r15) and the (?) 3.08 gears with .70 final drive ration on the 4speed auto.

Can yall help me out some?

Thanks,