You really need to get your car to a tech that knows what they're doing...sounds a lot like you've got some worn suspension bits, but you don't want to randomly start replacing everything...could get expensive.

AS to a kickdown "switch", look under the upper end of your accelerator pedal...see the switch? It sends a signal to the tranny to downshift, and the tranny will oblige as long as the downshift won't over-rev the motor.

As to your 1-2 shift, that's likely adjustable via a modulator, but I'll leave it up to the experienced techs here on the site to help you there.

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Best regards, Michael
'92 500E
'88 300TE