I've spent hours now searching this forum for information I can use to adjust the transmission on my 83 300cdt to eliminate flaring and bad shift caused I believe by alda adjustment.
I can only find conflicting "facts" and post after post which is answered by "run a search on _____ and there's lots of information." Unfortunately, every time one of these threads is shut down by this reply, it clutters up the searching process because it contains the keywords of the problem but no answer. This makes finding the right information impossible!!
So, does anyone know the actual answers to the following questions, so they can help everyone in the future who has this problem rather than frustrating them.
1. Is the transmission vacuum modulator on the back of the injection pump by the alda, or on the transmission, or are both of these vacuum modulators for the transmission?
2. Is vacuum fed to the modulator(s) through the device on top of the valve cover? What function does this contraption serve and how does it do it? I've read varying things, like that it softens shifts, it can be disconnected, it feeds vacuum to the modulator, et
3. How is a vacuum gauge and/or mityvac used in the calibration/testing of these transmission devices? I've read many times that you must use it, but on what lines, what readings to expect, etc.

I can't thank anyone enough who actually provides useful information on this subject. I know there are people on this site who are very skilled in transmission adjustment, but their information is impossible to find under all the dead-end threads.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

First of all, if I lived in gainesville, I would take it to Steve Brotherton who is the guru supreme of tranny adjustment. You can find his analysis here, probably in the stickies

But anyway-

1. The vacuum modulator is on the tranny. The vacuum control valve (VCV)is on the back of the IP.

2. Maybe. It depends on your particular car's plumbing. I have disconnected mine (along with the EGR valve) and run vacuum from the front fitting of the main line to the VCV.

3. I don't have a definitive answer as I only used a vacuum gauge to read the gross output of the vacuum pump and the vacuum circuit after the VCV. The tricky part for me was avoiding the 2-1 downshift clunk. I used the gauge to adjust the VCV.

I am not an expert. I just happened to get mine to work. Once. Break out the magic dust.

__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

Thank you for that advice. My dad took my diesel to continental back when he used it, but he switched to someone else because he said it was a "ripoff." You get what you pay for. I'll try taking it in there and see what Steve can do.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

I pretty much do my own wrenching and if I lived in Gainesville I still would do so. The tranny vacuum adjustments are pretty intimidating. I am sure Steve get the going rate for his work, but I would think this is an hour or two type job and he knows exactly how to tweak it. If you express an interest and tell him you are an active member of the forum, maybe he'll let you look over his shoulder (?) so you can fix it yourself next time. I'm sure he will also give you an assessment of the health of the tranny

__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

The DIY STICKY has lots of transmission adjustment info.

Danny

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

The miti-vac can be used just to measure vacuum and/or create it. Try this simple test to get some confidence: Disconnect the rubber line on the left side of the trans leading to the modulator (it's green). Connect the mitivac. Pump it once. Put your hand on the modulator and listen carefully. The needle should move and stop. Pump it again, the needle should go to a higher # and stop. You might be able to hear/feel movement inside the modulator. Pump it so the vacuum is about 25". It should hold there. Press the little release valve on the miti-vac and you should hear/feel movement in the modulator as the vacuum drops back to 0. The modulator pushes on a control valve inside the trans. As more vacuum is added, it pushes a little less.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

If you disconnect the vac line going to the transmission modulator, you should get hard shifts. All the vacuum shenanegans are to soften the shift when you aren't accelerating strongly.

If you still have flaring, you can replace the modulator and hope that's it.

If you get hard shifts with the vacuum line disconnected, then the vacuum shenanegans need to be adjusted. It might be the modulator on the tranny, or the vacuum control unit. With a vacuum guage Tee'd on the line to the tranny modulator, rev the engine. If the vacuum goes to near zero as the turbo spools up, it's the modulator (or tranny) that's bad.

If the vacumm controller output doesn't start with near full vacuum at idle to near zero at full throttle, it needs to be adjusted.

On your '83 I think the vacuum controller is on the rear of the IP, but on the earlier models it's on top of the valve cover??? I don't have experience on these cars earlier than '83. Follow the vacuum line from the tranny and it will lead you to the vacuum controller. Maybe your car has the '82 configuration?

This unit turns (edited) throttle position into vacuum looking like the manifold vacuum of a normaly aspirated engine.

You have to hook up a vacuum gauge and watch while you rev the engine, then diddle with the adjustments. On my car, a piece of dirt was clogging the vacuum restrictor right at the main line going to the brake booster. But my problem was shifts too stiff, not flaring.

The adjustment procedure is here:
http://www.babcox.com/editorial/ic/ic20242.htm

I put a ramp in the trunk and headed for the highway to adjust the new modulator after overhauling my tranny myself. I made a larger "key" so I could reach up there and turn it easier. Once it was just right I drove home and then put the cap on it.

Good luck with your tranny project!

Bruce McCreary
(2) '85 300Ds '83 300CD

Bruce,
This unit does not do anything wiuth turbo pressure.
It varies the vacuum applied to the modulator, dependant on THROTTLE POSITION only.
The Vacuum switches on the valve cover are used to ensure full vacuum is applied to modulator in "off pedal" situations, at least in our '82 & '84 Non-turbo 300Ds.
Regards,
Tony

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Yes, Tony's absolutely right, I slipped a brain cog. Vacuum is modified by throttle position only.

Bruce

Yeah, my searches hadn't turned up the DIY pages, but now I have it bookmarked. It turned out I fixed the problem myself by adjusting the vacuum control valve on top of the IP. There is a nut under the plastic cover and I turned it out to bleed out more vacuum and the shifts are quick, stiff, but not too hard. I also got the idea from Steve Brotherton's article to tighten the bowden cable a little bit to stiffen the shifts. I believe the VCV was the problem though. I may play with the modulator and bowden cable a little bit to make them perfect, but I've got it pretty much worked out now.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)