380SEL hard shifting problem

My 81 380 SEL shifts extremely hard in the lower gears,from first to second gear is the worst, the more accelorator the harder it shifts then gets progressively less significant from second to third and so on.I read in another fourm guestion you seggested checking the switch under the gas pedel, I've done so and it does not seem to be stuck. I've changed the tranny fluid and filter and now I'm stuck. Can you help?