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Non-responsive modulator
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.
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1981 300D 205,000 mi. |
#2
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Answer:
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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ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ Last edited by whunter; 01-05-2008 at 10:12 PM. |
#3
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That's an NA.....
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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 |
#4
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Thanks
Thanks Jimmy.
I am getting to old for fourteen hour days I wish you could come to the Detroit tech session. It is going to be tight scheduled tech in a shop that Johnson & Johnson could use for a pharmaceutical lab. |
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Quote:
I would love to make it up there for one of these. Um, but it would need to be July or August!!!
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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 |
#6
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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.
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1981 300D 205,000 mi. |
#7
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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.
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Nick ***** 2002 Sprinter 2500 140" High Roof : |
#8
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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.
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1981 300D 205,000 mi. |
#9
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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.
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Andrew '04 Jetta TDI Wagon '82 300TD ~ Winnie ~ Sold '77 300D ~ Sold
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#10
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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.
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1981 300D 205,000 mi. Last edited by Mattbob; 01-06-2008 at 05:03 PM. |
#11
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I've always found the modulators on this forum to be fairly responsive . . .
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" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century OBK #55 1998 Lincoln Continental - Sold Max 1984 300TD 285,000 miles - Sold The Dee8gonator 1987 560SEC 196,000 miles - Sold Orgasmatron - 2006 CLS500 90,000 miles 2002 C320 Wagon 122,000 miles 2016 AMG GTS 12,000 miles |
#12
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Quote:
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.
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1986 300SDL 201K Daily Driver 1984 300D In Progress 1989 240GL 196K Swedish Brick 1984 300SD -- Sold 289K ------------------------------ |
#13
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In my reading have I confused the terms 'vacuum' and 'pressure'. Less vacuum=more transmission pressure, and harder shifting.
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1981 300D 205,000 mi. |
#14
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Quote:
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.
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1986 300SDL 201K Daily Driver 1984 300D In Progress 1989 240GL 196K Swedish Brick 1984 300SD -- Sold 289K ------------------------------ |
#15
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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.
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1981 300D 205,000 mi. Last edited by Mattbob; 01-06-2008 at 07:32 PM. |
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