Hi all,

Today I fitted the K1 spring upgrade to try and illuminate a flare between 2nd and 3rd upsift on a 722.435. It has improved the speed it changes by at least half if not more but there is still a slight flare.

The shifts overall appear to be soft - could this be an issue with modulation pressure? And if so, would soft shifts be a result of too much or too little pressure?

I'm thinking I will have to get a pressure guage and some vacuum line so that I can hook it up to adjust pressure but where would I hook it up? And is the adjustment done at the IP or at the modulator itself?

Thanks for this.

Coincidently, all this trouble began after I replaced the vacuum pump.


1993 E300D
238,000K

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1995 E300 Diesel

The issue is with vacuum. You have too much of it.

There must be an adjustment on the 210 to reduce vacuum to the modulator. You'll need a vacuum gauge to determine where you are at the moment and you'll want to drop it by about 2" and take it for a test. All vacuum adjustments need to be done in small increments and they can't be done without a gauge.

Brian,

Thanks - I will get hold of a guage. Have you any idea of the name of a good brand and where I might get it from?

I will have to get it out of the US as there are very few places here in Australia that would stock such a thing.

Also, as for the adjustment, is it done down by the transmission itself or up at the IP?

I can see a black hard vacuum tube coming down from the engine bay going into the right hand side of the transmission into an orange plastic gizmo (modulator?) with a white plastic cap at the top.

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1995 E300 Diesel

Any vacuum gauge that will read to 20-25"Hg will do. Check the vacuum signal from the vacuum control valve (VCV) on the side of the IP to the transmission modulator. The like will likely have a green cylindrical damper.

I'm not sure what Brian means to adjust. I say this because a 93 300D, assuming that's what you have, doesn't have a transmission vacuum amplifier, a blue saucer in... well... who knows where it is in a RHD car. In my mind the VCV is something you set in a static condition once. You adjust modulator pressure to specification by turning the T-handle covered by the rubber cap on the modulator. Lift the T-handle past the castellated retainer and turn. To do this you should have the specification and a pressure gauge hooked up to the test port on the transmission below the modulator. It probably won't hurt to turn the T-handle CCW a castellated retainer notch or two to determine if that improves shifting. If your car has a transmission vacuum amplifier, then there is an adjustment point as Brian describes.

Sixto
87 300D

I missed the fact that it's a 124 and not a 210. I presume the 602 and 603 are similar?

Does the 602 use the amplifier (blue flying saucer)? If so, there's a bit of adjustment via the screw on the bottom...........but, it is not significant.

The final resort is to increase modulator pressure, but I loathe to advise this until all vacuum solutions are exhausted.



To the OP:

It would benefit for you to find a "Mityvac" which can both measure vacuum and also supply hand held vacuum for testing. I'd wager that such a device is available there.

Will get a mityvac also. Yes, it is a W124 but with an OM606 N/A.

How do you get the white plastic cover off the modulator? It looks very old and brittle from the heat and I just don't want to pull it incase it breaks.

I can see a white device on top of the IP, is that the VCV? And then a green flying saucer thingo on top of that.

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1995 E300 Diesel

Apparently, my original error was a case of brilliant clairvoyance............I was thinking a 210 with a 606............sheer luck.

Can't give you any advice on the 606 as to whether you can do any vacuum adjustments. Need those fellows to chime in.

I would not start with the modulator...........leave it alone until you get a Mityvac and see what the modulator gets for vacuum.

Any W124 606er's that can suggest anything?

If I get hold of a pressure guage, I am guessing I'll have to measure the pressure down by the modulator whilst driving.

Where would I find information on what pressure I should have i.e whilst at idle and whilst driving?

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1995 E300 Diesel

vacuum


the vacuuum



vacuum


Come on now............we've learned you in this stuff..........

Ha Ha! Yes, that is the state of my mind today. A combination of a late night and a two year old early morning riser = not much sleep

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1995 E300 Diesel

.........ahh........I know the feeling.........I look at some of the things I post the next day and wonder...........WTF..........that alcohol really degrades the accuracy...........

I have no fears, however, TF will always catch me out............

C'mon Brian, you know he meant pressure in the absolute scale

Wow, I didn't know the 606 was available as early as the '93 model year. Start a new thread with 95 E300 in the subject line. That'll get the attention of folks with the most similar configuration offered in the US.

I found the attached picture of a [claimed] 95 E300 IP on eBay. There are enough differences between this IP and the 603 IP that I can believe it's a 606 IP. It has mechanical throttle actuation which suggests it didn't come out of a 210. The VCV is the device hanging on the port side of the IP with a white plastic cap. It is held by two bolts (10mm wrench) through slotted ears. My recollection of the adjustment procedure is to hold the throttle at WOT, I strongly recommend with the engine off , and twist the VCV CW as you view it from the port side until you feel some tension. Batten and go.

None of the US Diesels for the '93 model year have a transmission amplifier. Without it, I remain puzzled by how Brian expects to modify the vacuum... err... pressure signal to the modulator. AFAIK adjusting the VCV shifts the timing of the vacuum signal, not the quantity of vacuum.

Brian, maybe what's vacuum turns to pressure in the southern hemisphere.

Sixto
87 300D

Attached Thumbnails

 

Thanks for the pic sixto..
I might try to take cross over pipe off tommorow and take a picture of my IP because from memory mine looks a little different around the VCV.

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1995 E300 Diesel

Thanks for that Sixto.

The adjustment procedure for the VCV appears to be identical to the 603. It does not provide any capability for the technician to tune the output, unfortunately.

And, without the amplifier, I agree that there is no possibility of shifting the vacuum curve to the modulator.

So, all this talk about pressure/vacuum is largely moot on this engine.

I would like to see what vacuum level is actually going to the modulator. If the VCV isn't working correctly and the output is higher than spec, it would be of no benefit to chase modulator pressure and attempt to reduce it when vacuum is the culprit.