Author Topic: Shifting at the dots under WOT  (Read 376 times)

raueda1

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Shifting at the dots under WOT
« on: 29 June 2020, 05:42 PM »
My car has never shifted at the speedo dots under WOT.  The tranny/throttle rod now seems to be in the sweet spot for low speed and partial throttle shifting and general drivability.  Kick-down switch is also fine. 

That said, I've never gotten the car to upshift at the speedo dots.  Not even close, always 15-20 mph short, maybe more.  By my reckoning the dot is pretty close to redline.  I wouldn't want to press it that hard very often, but I'd like to know I could.   

So what governs the WOT upshift points?  It doesn't seem to be the control rod.  Maybe the vacuum modulator?  Something else?  AFAIK the transmission is tip top and I don't have any vacuum leaks.  What to play with? Any insights appreciated, cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Shifting at the dots under WOT
« Reply #1 on: 29 June 2020, 07:08 PM »
Dave looking at the transmission manual the 1-2 upshift is at 79 km/h and the 2-3 upshift is at 144 km/h under full throttle.  I see the dots on the speedo do not correspond with these numbers so not really sure which one is "right" ???
Daniel
1977 450 SEL 6.9 - Astralsilber

ptashek

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Re: Shifting at the dots under WOT
« Reply #2 on: 30 June 2020, 03:02 AM »
Your car will never shift at the dots for a simple reason - they're not indicating shift points.
They indicate the maximum speed you should drive at in a given gear when shifting manually (using S/L/D positions).
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revilla

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Re: Shifting at the dots under WOT
« Reply #3 on: 30 June 2020, 03:38 AM »
Correct.
The dots (orange bars) are used for example when using the transmission lever in assisting breaking (down-shifting 4-3 or 3-2).  If you are in ‘D’ on 4th gear and you go to ‘S’ to force 3rd at a speed above the dots you’ll basically force the engine into red zone revs. Not good.
Cheers
Robert
W116 1977 280SEL & 1979 280SE

raueda1

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Re: Shifting at the dots under WOT
« Reply #4 on: 30 June 2020, 09:08 AM »
Thank you gentlemen, this is actually great news.  No idea where I got the idea that the dots were WOT shift points, but the notion was stubbornly fixed in my brain.  So all was well all along. Nothing beats solving a problem by learning that it isn't really a problem!
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

UTn_boy

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Re: Shifting at the dots under WOT
« Reply #5 on: 30 June 2020, 09:20 AM »
And remember that the modulator valve ONLY controls how soft or hard the transmission shifts. 
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raueda1

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Re: Shifting at the dots under WOT
« Reply #6 on: 30 June 2020, 11:24 AM »
And remember that the modulator valve ONLY controls how soft or hard the transmission shifts.
Great!  Another problem solved without ever leaving the couch.  Must be a first. Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Randys01

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Re: Shifting at the dots under WOT
« Reply #7 on: 02 July 2020, 07:31 PM »
I have observed over the years the red line on 6.9 variants sits between 5 and 5 and a quarter. I am yet to determine a pattern to this but I bet the max rpm per gear tabs on the speedo are not varied accordingly!! :-\

s class

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Re: Shifting at the dots under WOT
« Reply #8 on: 02 July 2020, 11:04 PM »
The 5000 or 5250 redline on 6.9s is an early / late thing as far as I know. 

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