With a non-loc-up automatic, you will never get the at-speed rpm to agree with the calculated rpm......... because the TC is slipping always slipping. It's a fluid coupling not a clutch.
Next time you are out cruising, make note of the tach reading. Then simultaneously feather the brake and gas pedal to maintain your cruise speed and watch the tach. Next increase your speed a couple of mphs then lift off the gas, again watching the tach as the mph comes across the chosen cruise mph.
Don't be surprised to see 400rpm or more difference.
