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Car Forum / Mercedes-Benz Cars / November 2005

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1986 500sel  transmission prob

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jb - 14 Nov 2005 00:27 GMT
I have a 1986 500sel AMG that is shifting terrible. It will only shift if
RPM's are high, over 3000 and you let off accelerator.

Fluid is OK. I checked the modulator valve with a vacuum pump to make sure
it would hold a vacuum and it does. the vacuum gauge on pump (with engine
idling) showed the vacuum to be in range. The filter has been replaced also.

Bad modulator valve??? Any ideas??? It just started doing this suddenly. We
don't drive this car very much either.
T.G. Lambach - 14 Nov 2005 01:12 GMT
The modulator controls the relative softness (or harshness) of shifts -
not WHEN shifts occur. (More vacuum to the modulator makes shifts softer.)

The transmission is "told" the engine's throttle position. I don't know
how this is done on your model, older diesels have a rod or cable from
the throttle linkage down to the right side of the transmission. I
understand other models use vacuum to accomplish the same and suggest
your car may be one of these. A broken or leaking vacuum line would be
the suspect if that's so.

Others may have more specific suggestions on this subject.
jb - 14 Nov 2005 02:23 GMT
Well, mine is a gasoline engine, not deisel.  Thanks.

> The modulator controls the relative softness (or harshness) of shifts -
> not WHEN shifts occur. (More vacuum to the modulator makes shifts softer.)
[quoted text clipped - 7 lines]
>
> Others may have more specific suggestions on this subject.
Karl - 14 Nov 2005 02:35 GMT
I was going to say you do have throttle pressure control but......

You say you have a 1986 500SEL???
In the USA, 1985 was the LAST year of the 380/500 series. 1986 was the first year of the 420/560
series.

What exactly do you have??

> Well, mine is a gasoline engine, not deisel.  Thanks.
>
[quoted text clipped - 9 lines]
> >
> > Others may have more specific suggestions on this subject.
jb - 14 Nov 2005 02:39 GMT
It is a grey market euro car.  500 sel with AMG package.

> I was going to say you do have throttle pressure control but......
>
[quoted text clipped - 17 lines]
> > >
> > > Others may have more specific suggestions on this subject.
Karl - 14 Nov 2005 02:52 GMT
Look at the right rear corner, down at the in-board side of the valve cover. Below the black hose
sticking out and going to the air cleaner.
Do you see a round silver rod coming up from the transmission? It has 2 sliding tabs on it.
The sliding tabs are part of the piece that snaps into the gold colored bushing. Is it snapped in
place?

> It is a grey market euro car.  500 sel with AMG package.
>
[quoted text clipped - 25 lines]
> > > >
> > > > Others may have more specific suggestions on this subject.
jb - 14 Nov 2005 03:05 GMT
it's late here in georgia, I'll check that out tomorrow. thanks.

> Look at the right rear corner, down at the in-board side of the valve cover. Below the black hose
> sticking out and going to the air cleaner.
[quoted text clipped - 31 lines]
> > > > >
> > > > > Others may have more specific suggestions on this subject.
Paul - 14 Nov 2005 12:21 GMT
Check the "Kick Down Switch" under the accelerator peddel.  They are known
to stick and cause this problem.
Paul
> it's late here in georgia, I'll check that out tomorrow. thanks.
>
[quoted text clipped - 44 lines]
>> > > > >
>> > > > > Others may have more specific suggestions on this subject.
jb - 19 Nov 2005 17:58 GMT
no. it isn't stuck. is it possible that is bad? would it be same symptoms?
thanks

> Check the "Kick Down Switch" under the accelerator peddel.  They are known
> to stick and cause this problem.
[quoted text clipped - 47 lines]
> >> > > > >
> >> > > > > Others may have more specific suggestions on this subject.
jb - 19 Nov 2005 18:02 GMT
none of that stuff.  It does have a cable on that side from accelerator
setup on engine to the transmission. cable is connected and not broken.

> Look at the right rear corner, down at the in-board side of the valve cover. Below the black hose
> sticking out and going to the air cleaner.
[quoted text clipped - 31 lines]
> > > > >
> > > > > Others may have more specific suggestions on this subject.
saeef - 20 Nov 2005 14:47 GMT
jb,

How many miles the trans has? Hate to say this but maybe it is time to
overhaul it. My 560 was shifting very rough and sometimes did not want
to shift. It turned out it had worn internal components. I overhauled
it.
jb - 21 Nov 2005 03:11 GMT
180K.   I know that is a lot, but it was working perfectly  until  I took it
to a garage to have a leaking seal replaced. Been bad since I got it back.

> jb,
>
> How many miles the trans has? Hate to say this but maybe it is time to
> overhaul it. My 560 was shifting very rough and sometimes did not want
> to shift. It turned out it had worn internal components. I overhauled
> it.
 
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