420 sel transmision revs between shifts
 

I just test drove for the first time my "new" 1991 420 SEL after a 560 motor installation. I never drove the car with the 420 motor. The transmission was rebuilt a few thousand miles ago. Everything felt great but when the car shifts from 2nd to 3rd the engine revs an extra 700-800 rpms then shifts. It sounds like someone blipped the throttle. The shift from 3rd to 4th the engine revs an extra 200-300 rpms then shifts. The 2nd-3rd shift problem is much more noticeable than the 3rd-4th shift. The shifts are smooth you just hear the engine rev. Is there an adjustment for this?