When trying to firm up shifts, I turned the modulator key one notch counterclockwise. This had no affect. So I turned it two more, still no affect. I have extremely soft shifts with flaring, and had pulled off the vacuum to the trans earlier, with resulting very hard shifts.

Why is the key not doing anything? Or am I adjusting in too small of increments.

__________________
1981 300D 205,000 mi.

It is very possible the vacuum modulator has died from age.

Item Number: 1232700679
Main Category: MB
Sub Category: Transmission
Description: VACUUM MODULATOR VALVE
Weight: 1.000









Have a great day.

__________________
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That's an NA.....

__________________
Jimmy L.
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Thanks Jimmy.
I am getting to old for fourteen hour days
I wish you could come to the Detroit tech session.
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I would love to make it up there for one of these. Um, but it would need to be July or August!!!

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

So those increments usually produce results? I had read one post that someone suggested a turn (360 degrees?) and I believe another one that said vacuum is raised/lowered 2 bar each notch.

__________________
1981 300D 205,000 mi.

I strongly doubt that...especially since vacuum isn't generally measured in bar...but inches of mercury (or the metric equivalent)

And 2 bar = 29.4psi...that's a lot



On a sidenote...I did the same thing with my modulator...and it helped a wee bit, but not a whole lot...so I am going to try installing a restrictor valve (boost controller off the Subaru) and see if that will make the vacuum signal calm down a bit.

__________________
Nick
*****
2002 Sprinter 2500 140" High Roof :

That sounds like a good idea. My VCV is non-adjustable, and since the trans is getting too much vacuum, I was hoping for another way of restricting some of the 'flow'.

Because the transmission reacted as predicted when I disconnected the hose does that mean that the modulator is 'functional' but only it the spot it was currently in...something is broken that inhibits adjustment?

I just read another post in the 'it's critical thread' that suggested three full turns... I don't think my measley three notches would do anything.

__________________
1981 300D 205,000 mi.

You can test the modulator with a mity-vac. Pull vac on the modulator and it should hold for a few seconds then slowly bleed down. If you can't get any vac or it bleeds off quickly then the modulator is bad.

__________________

I'm getting a mity vac from work )mcmaster= on Monday.

She started slipping bad today between 3-4. This went away on its own. I popped off the vacuum to the trans completely, and I no longer get the bone jarring shift, it didn't seem to have any affect. What would cause that? The only thing that has changed (I think) is the modulator position, and with the vacuum disconnected that shouldn't matter.

__________________
1981 300D 205,000 mi.

I've always found the modulators on this forum to be fairly responsive . . .

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You should be turning the modulator key clockwise to increase the trans pressure and increase the firmness of the shifts. One complete revolution of the "T" key changes the pressure by about 0.4 bar.
So, you can get about 6 psi change in complete turn.
I have always moved the key in 1/4 turn increments and tested again.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

In my reading have I confused the terms 'vacuum' and 'pressure'. Less vacuum=more transmission pressure, and harder shifting.

__________________
1981 300D 205,000 mi.

The pressure referred to is within the transmission in PSI.
The vacuum in inches of Hg is the vacuum applied to the trans modulator.
There is a good write-up on the subject at -

http://www.continentalimports.com/ser_ic20242.html

You really need to get your vacuum supply correct to the modulator
then , if needed , adjust the modulator.
The adjustment on the modulator is changing the dynamic pressure in the transmission in response to vacuum supplied to the modulator.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

My on the trans. line to teh modulator is 18 at idle and only drops to 15 at full throttle. My understanding was that the vcv controls the range, my vcv is the non adjustable kind.

Note that I have my egr and 3/2 out of the equation.

__________________
1981 300D 205,000 mi.