Upshifting in an automatic

[Cees Klumper]

Well, I am still convinced that my trans used to (before putting in the rebuilt engine) shift up at higher speeds when extra throttle was applied (because extra pick-up was needed) without engaging kick-down, exactly as any other automatic I've ever driven does. So Joe's research is consistent with the behaviour of all of our cars here (except mine) but I will continue to investigate why my transmission now behaves like all the others and I will try to get it to go back to the way it operated before, because that to me seemed much better: not having to manually downshift or floor the accelerator to get the car to get up and go ...

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[George Davis]

Leaping in with random thoughts and questions -

I assume the vacuum modulator has something to do with when the transmission upshifts?

Low vacuum generally means high load (throttle more open), and high vacuum generally means low load (throttle less open).  But might not engine condition affect vacuum, too, with a worn engine having less vacuum?

Perhaps in Cees' case, the old engine had less vacuum to begin with, and when the throttle was opened further the vacuum went low enough to delay the upshift?

Is the vacuum modulator adjustable?

Is there life on other planets?

George Davis
'69 280 SL Euro manual

[Cees Klumper]

Hi George - my thoughts exactly. When I change my ignition timing enough, the upshifting points change significantly, so vacuum has its effect on shift points.
And, yes, there probably is life on other planets, but it's probably not much better than here!

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic