As long as the Rubber Sleeves fit snuggly on the Vacuum Valve and Trans Modulator Nipple and on the Plastic Tubing you use I don't think it matters what size the Tubing is. I say that because the inside diameter size of the Nipples is going to be where the restriction is.
That means as long as the ID of the Tubing is slightly larger than the ID of the hole in the Nipples the tubing should be fine.

If you are worried about the Tubing/Line lasting a long time you could could replace the whole thing with Silicon Vacuum Hose; that would be replacing the 2 rubber sleeves and the Plastic Tubin with Vacuum Hose. The Silicone won't rot or crack like Rubber does and there is no Exhaust Pipe or Exhaust Mainfold that the Hose could get burned on.

I accidently disconnected the Vacuum Line to the Modulator and when I drove the Car the Up Shifts were close to the same but the Down shifts were extremely harsh.

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84 300D, 82 Volvo 244Gl Diesel

trara - take a look at the second pic in the first post. see the green thing? thats my modulator. the bolt you need to take off is to the rear of the modulator, a little closer to the ground, passenger side.

i dont think its radically different for a 722.118 and should be the same.

good luck and i hope this helps -
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

So I thought i;d post somethings i figured out...
I finally figured out which bolt it was by look at Stretch's monster diy on the 718.222 where he labels all the ports. its in a pretty tight spot that was a pain to get to, next to the modulator towards the ground nearer to the front of the car tucked in a corner.

Also i couldn't find a spare banjo bolt which stumped me for a minute but found a diy about adjusting the modulator on Scribd and he mentions that there is an adapter for a M8 X 1.00 in the Harbor Freight oil pressure gauge kit($25 but it comes with the gauge and a bunch of fittings), and voila! it fits into the modulator test port. It goes to 1/8" female so you have to add some more fittings to hook it up to the hose. I ended up using a fitting from Autozone that is male 1/8" to a 1/4" barb. I tried at first to piece something together from the different fittings in the kit i bought, but all the combinations make something too big to screw it into the tight space. but the autozone fitting kept it small enough for me to still maneuver a wrench in there. So I finally got everything all hooked up and adjusted the pressure to 3.0 (it was really high at like 6.0)

and Thanks much to everyone out there for helping me piece together a solution. I'm gonna test drive and then maybe have to work on linkages.

Nice writeup, THANK YOU ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Great write up. And I will say that, for somebody with no access to a yard car for banjo bolts, I was able to do this all with the fittings/hose/gauge in HF oil pressure test kit. It was cheap!

Hi,
my name is Matthias, I am located in Germany and owner of an beautifull W116 300SD build 1980. Yesterday I have check my modulation pressure and set it form 5,2bar to 2,8bar (engine idle in park, vacuum of) as discribed in this thread. After a test drive I set the pressure back to prox. 4,6bar because the transmission shifts too smooth an slips during the shiftings. After that I have make a test drive and the pressure was 2,9bar between 40 and 60kmh without vacuum.(Thatīs o.k. in my opinion)
With the installed vacuum line the pressure at idle was 1,5bar.
Know my questions:
-Are there any known problems by testing the pressure at idle for these transmission type?
- Is the pressure during idle and installed vaccum line all right? (I have read something near 0?)
My transmission is an 722.120 02 022103 with an red modulator on the right side.
Thx for your support and sorry for my bad school english ...
Best regards Matthias

I think that pressure should be checked at 50kmh as the FSM says. I checked mine today and noticed a big difference of pressure at idle in park and lower pressure with accelerator depressed.or (take-up accelerator linkage free play off idle) Obviously, when one depresses the accelerator it reduces vacuum to the modulator via the VCV on the IP. The modulator moving changed the internal pressure of the fluid. My modulator is not leaking vacuum either I had checked it.

Were you moving? Once the vehicle is moving and transmission engaged the pressures all balance each other out to the same as idle.

Back when I wrote this (10 yrs!) I asked a few benz specialist mechanics and they all said they have never heard of anyone doing this at 50kmh - the reading is the same as it is at idle for the purposes of these vehicles. After taking this reading I have never had trouble then putting a transmission into a happy shifting place.

I also think that driving while having open lines to the transmission, trying to read a pressure gauge and maintain a fairly fast speed at the same time is a recipe for disaster.

cheers,
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I've done this pressure test - it works perfectly fine while in Park, and you don't need the throttle movement and vacuum regulation of the VCV---> modulator at all to test the pressure of the modulator. In fact, you disconnect the vacuum line completely when you are testing the pressure at the port.

good ol Ken at the M source says you need to be running at speed, and offers a kit to run the line up through the firewall/door somehow in to the cabin. But honestly, it's not needed as I was able to get a proper reader and corresponding behavior.

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Andrew
Montclair, NJ
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1982 300D Turbo
120k
Petrol Blue Green

I was both moving 30 mph and stationary. I got a different reading when the accelerator was depressed. I didn't see it written to remove vacuum line for the VCV in the write-up. Diving and reading a pressure guage is the the same as I do when checking the turbo boost.

Follow the instructions .

After all, THEY made the damn thing .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Who is that addressed to?

_You_ of course .

Doing things by the book should be the default option until you're comfortable and knowledgeable enough with the job to try different things .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I think your confused. Can you show me where I said to try anything differently. I am the one advocating to follow the FSM.

I'm not the confuddled one here ~

You said follow the FSM and I agreed .

Now you're trying to twist what I said into God alone knows what .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better