so tonight will be the moment of truth...I will reinstall my VCV and test the vac system - which has to work - I have tested, removed and replaced almost every component.

Here are the steps I am going to take:

1.) Reinstall VCV, check system with MityVac, car off. Want to see bleed equal to that of my VCV bench tests
2.) Turn car on, T in vac gauge at the transmission vac line.
3.) Look for 15mgHg at idle, dminishing smoothly to zero at full throttle.
4.) Ideally, if I was able to, here is where I'd adjust the range of the vacuum signal with my adjustable VCV, if I had one
5.) Adjust transmission shift cable to proper default setting. I understand this to be slight amount of tension at min throttle (Brotherton article).
6.) Ideally I'd check the modulator, but I have no idea what the default setting is, so I'll just have to...
7.) Drive and hope. Make adjustments based on shift timing/quality.
8.) In all likelihood, report back here with new transmission problems.

Any comments, or anything crucial I'm missing?

As I have alluded to before, if I get this all sorted out I'll do a write up with pictures that sums this thread up...I get this vacuum thing now. It's not that bad once you get it - but terrifying initially if you don't.

-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

Personally, I believe that 15" is too high on these vehicles. The shifts are all mushy and, if the trans is old, you'll get some flare on the 2-3.

I've got the SD at 8" and it's got some crisp shifts.......bordering on banging when stone cold. I like it that way.

Brain - thanks for the tip, Ill look for less tonight.

I think I have found the adjustment you all have talked about on the VCV. Its talked about on the Mbz.org transmission tutorial in a way i realized what I was missing...

http://articles.mbz.org/transmission/adjust/

To adjust my VCV you just need to turn the shaft a few degrees one way or the other. I didnt realize that dome came off. I was removing something else when Brian directed me to take the dome off.

Now I know for tonights tuning exercise. Sweet. It's a good feeling to now know all the knobs I need to turn, and exactly what does what before I go into battle.

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

the article i referenced in my previous post talks about making an adjustment of the throttle linkage so that it is 10mm from the stop pin. i made the tool, a 20 mm diameter disc that fits over the stop. but, im confused as to exactly what i am trying to adjust to 10mm. the flat of the lever to the *top* stop pin at idle? that seems awfully far away from what i currently have, i dont even know if i can extend my linkage far enough to achieve that. this must be what its referring to, i cant see what else it could be talking about. i want to get this right before i start mucking with the VCV adjustment.

FWIW, i have 15.5mmHg T'ed into the modulator vac line, diminishing to 0 at full throttle just like it should (small victory). took it out for a quick test drive and my shifts were still harsh. as i understood it earlier from Brian, i should of had flaring if anything if my vac was way too high like that.

also FWIW, the mbz.org article says you should have 5.5-6.5mmHg at the modulator at idle, the brotherton and sun valley articles say 10-15 mmHg.

i feel like im almost there, i just need a little more help to get over the top...i really want to try to do the adjustments by the book instead of ballparking stuff like modifying the shift quality at the modulator at this stage of the game.

__________________
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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 here's what i ended up doing...

reading the actual mercedes tech manual for the VCV test:
http://www.peterschmid.com/

1.) adjusted the throttle linkage that goes to the VCV to 11.8cm
2.) turn on engine. linkage still not attached. saw reasonable vac readings T'ed into the trans line. 15mmHg at idle, smoothly diminishing to zero at full throttle...just like you read about. woohoo!
3.) from peterschmid mercedes tech manual - made my own 10mm radius disc from cardboard and put it on the upper VCV stop.
4.) moved VCV lever up to edge of disc, noted 7 mmHg. Mercedes spec calls for 4.3mmHg at this point.
5.) adjusted VCV by popping dome off and turning the shaft slightly with 8mm ignition wrench until I got 4.3mmHg with the lever at the 10mm cardboard calibration point. Now i have 10mmHg at idle.
6.) replaced dome on VCV. reattached throttle linkage...not trivial...
7.) adjusted bowden shift cable per sun valley mercedes instructions.

The vacuum system, to the best of my knowledge is now working and delivering the right signals to my modulator. But...my MB still shifts consistently hard on all gears and shifts. The hardness of the shift also doesn;t seem to change based on throttle position. Not that much different than before. Doh. I adjusted the bowden cable about one turn or so to make shifts earlier, around 2200 rpm or thereabouts.

Next I will turn my attention next to the modulator 'T' to soften the shifts...unless there is something that I am potentially missing or additional diagnostics I can run?

Also - when I shift into R and D, the car lurches back and forward respectively, like its snapping to attention. Is this normal for these cars? Someone told me it is...just want to confirm.

__________________
-------------------------------
'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

You've done an admirable job of setting the VCV per the specs.

However, I tend to ignore the specs and set it by feel. The SD demanded a setting of 8" at idle to have a crisp shift. However, it appears that you need a much higher setting to get rid of the harshness. So, I'd advise increasing the setting at idle to 15" or more, in an attempt to soften the shifts.

If you find that the VCV has no effect on the shifts, please confirm this by removing vacuum completely from the modulator and see if the shifts get any firmer than they currently are.

If there is no change across the operating range with various levels of vacuum, then it's most likely due to a failed modulator valve. I would advise you not to adjust the modulator pressure at this time.

Thank you Brian...

I took the car for a test drive when it was at 15mmHg idle point and it was pretty much the same as my 10 mmHg 'factory spec' setting. i would imagine at the 15mmHg I should have noticed *much* softer shifting.

new modulator valve it is.

looks like a pain to replace, but i have seen it documented repeatedly here...bring it on.

dd

__________________
-------------------------------
'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

DD - Here is my take on the instructions you posted from mbz.org, but first take a fresh look at the photo I POSTed a short while back [in POST #141]:
http://www.peachparts.com/shopforum/attachments/diesel-discussion/38850d1165336744-its-critical-how-you-set-your-transmissions-vacuum-system-your-diesel-mbz-vcv-100_5283-ed.jpg
I believe that first [with the engine shut down], you need to make sure that your VCV-to-Throttle linkages are adjusted for " max throttle " leaving only ~1mm between the VCV's " tang " and the metal stop pin in the body of the VCV.

Then you place the 20mm dia. disc over the metal stop pin [ on the right in my photo ]. This I believe simulates the idle position. Start the engine and [IF necessary] close the throttle to where the metal " tang " contacts the disc and hold this throttle position [possibly a fast idle] with a bungie cord or other means while you make the internal adjustment to the VCV parts under the plastic dome.

Brian - If you are out there and can confirm whether we are on the right track in our understanding of both the external and internal adjustments for the VCV... please jump in here!

Again "DD" I never had to adjust my VCV in this fashion for I was able to get it to function by varying the vacuum input with smaller orifices. I wrenched my back out doing a dashboard dive while working on my Son's MBz so I canNOT bend over the engine compartment to try and follow this exercise up close on one of our cars!

Which raises the question "DD"... have you found the vacuum diagram for your car and do you have the restricted orifices [if ANY] installed as called for in the diagram. ?

The vacuum diagram for your 1982 300D Turbodiesel is at:
http://www.peterschmid.com/vacuum/1977_1985/617_95/1981_1984.jpg
and yes #63 there shows a restricted orfice limiting the vacuum being fed to the "Y" connector, the VCV bleed, and the line going down to the modulator.

The diagram also gives you sizes for the various color orifices but does NOT tell you what color/colors should be used! If I remember correctly I worked mostly with the smallest of these listed on this diagram.

Oh, make sure you reinstall the green dashpot [#72] and test it first to make sure there is no leak in this empty plastic chamber with input/output orifices!
Regards,

Sam, if the modulator isn't functioning, all the efforts of precision setting of the VCV are for naught.

Test drive it with full vacuum and test drive it with no vacuum. If the results are the same, no sense bothering with the VCV until the modulator responds to vacuum.

When I shift into R and D, the car lurches back and forward respectively, like its snapping to attention after a short delay. Is this normal for these cars? Someone told me it is...just want to confirm.

__________________
-------------------------------
'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