a buddy of mine has a 84 sel 560 (got it for 500 bucks runs great) but the trans will not shift right all te time if your driving normal it will usualy work fine but if you get on it it acts like the kick down cable sticks from then on it will only shift when you hit redline.

we have disconected the kickdown and it moves freely and disconecting it and pulling it all the way out or pushing it in dose not change any thing.
The only thing you can do to get it to go back shifting right is to let it sit for about a week or 2 then alls fine.

If you get it to shift right and disconect the kickdown it will shift very early and hard. but still if you get on it it will go back to not shifting till redline.

Its fun to drive that way the damd thing will fly, but he needs it to be a dd and you cant drive around town at 5k all day.

 

There should be adjustment key behind small rubber both in the middle of vacuum control valve mounted on the side of your transmission. The key is a T-shaped blade with slots around to hold it in position. You should hook up pressure gauge to tranny and adjust to certain pressure for correct shift timing. First check the vacuum line for cracks or damage, make note of the key's original position and adjust by 1/4 turn max. and test it out. It should be same tranny as my W126 '80 280SE Euro. I believe I have a manual for this transmission, I will check the trouble shooting section for your symptoms.