I just replaced a bunch of vacuum lines in my 87 300d with basic metric rubber vac line. The car now shifts too soft on all shifts, with a noticeable flare from 2-3. If I understand flare correctly, it is a racing of the engine and a prolonged soft shift, right? Well I wonder if I might have inadvertently eliminated one of those orifice thingys I have read about... seems like I have too much vacuum. I wonder if the vac orifices or some other vac adjustment have been messed with to increase vacuum and now I have eliminated a bunch of little leaks by replacing dry rotted cracked hoses so now I have too much vacuum and need to reintroduce some orifices or turn the vac down some other way? The car came to me with a new vacuum pump, so they must have had some problem. I also replaced my alda which was screwed up and the car seems to have a bit more power now so I don't know if the soft shifts and flare have anything to do with that but it seems since I was screwing with vac lines that must be the problem. I also noticed the vacuum control valve on the side of the injection pump near the back had a long crack in the rubber elbow vac fitting that sticks out the side of it. I tried to pull it out but it ripped and I replaced it with a bit of vac hose stuffed in the hole, seems to seal ok. Any input appreciated; I am going to go study my manual to try to find out about these orifice things.

If you have a vacuum gauge, it would be beneficial to T into the line to the transmission and read the vacuum at idle. That line runs from the top of the vacuum amplifier (blue flying saucer).........the side port on the top.........

Or, you can just wing it. Remove the vacuum amplifier and you'll find an adjusting screw under the black plastic M/B cap on the bottom of the unit. Turn the plastic hex screw fully clockwise and reinstall the vacuum amplifer. You'll need a 4mm socket for this screw.......don't try it with anything else.

Take it for a drive and see how you like it.

Thanks for the tip, Brian. I tested my vacuum at the vacuum control valve, after the little plastic can the manual calls a damper. It was right on at a little over 10 inHg. The manual specifies 385mbar +/- 25 which converts to 10.6 to 12.1 inHg. So what should I be reading if I tee in where you suggest? How do I know how much to tweak the screw? I also was wondering about the "restrictors" as the manual calls them. I think these are the same as the "orifices" some people talk about? I am not sure I have a proper vacuum diagram in my factory engine manual for my particular engine, since they all seem to include the air recirculation valve, which I don't have. I am not sure therefore if I should switch my orifices to match the colors in the manual diagrams. Anybody know the proper colors for restrictors/orifices for an '87 300d with no air recirculation valve? The restrictor I currently have coming off the vacuum control valve is green and the diagrams I have specify blue...

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87 300D 162,000 miles: It's not just a car, it's an adventure!

Mine has been having a flaring problem also. It also will do a stacked shift, where 3rd-4th comes immediately after 2nd-3rd. The wierd thing is sometimes it will shift fine. I did turn the bowden cable clockwise, and turned the adjuster on the transmission modual clockwise, and that seemed to help temporarily, but after a 1,000 mile drive it's back to horrible flaring again. Mine also has the green vacuum restrictor. There is supposed to be a way to adjust shift quality by loosening the two bolts that hold the vcv on, then twisting it around, but I tried twisting it both ways and it only made things worse. The same went for adjusting the nut on the amplifier. I am kind of wondering if either the vcv or the modulator is bad on mine, but not sure how to test that?

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

T a vacuum gauge into the output from the vacuum amplifer (blue flying saucer) to the transmission and read the gauge while driving the vehicle.

Report back on the vacuum under various conditions........idle........1/2 pedal.......3/4 pedal.........and maximum power.

Are these readings made while standing still, or while the car is in motion?

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

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I turned the plastic screw fully clockwise as you suggested, Brian, and my shifts did firm up some but still I had flaring. I teed into my vac amplifier where the line goes to the tranny and measured 13.5 inHg at idle 750 rpm. Under light acceleration i measured 13.5 inHg and shifted with a very slight flare. Under lt-mod acceleration I measured 9 inHg and got a 2-3 flare which shot my rpm from 2750 to 3250 before completing the shift. Under moderate acceleration I measured 7 inHg and got the same 2-3 flare and engine racing from 2750 to 3250. Under heavy acceleration I got 0-4 inHg and my shifts were soft with the 2-3 shift being slightly long but no engine racing. My vacuum control valve appeared to be turned fully counterclockwise, so I adjusted it clockwise as the manual suggests, in park at full throttle until some resistance is felt. Once I completed this adjustment I noticed that a little line on the vcv lined up with a line on the injection pump almost as if someone had adjusted the vcv and marked this as the correct spot to be in. This adjustment improved my shifts further, and I don't get the same 2-3 revving flare but all the shifts do still feel a bit soft. I checked my orifices/restrictors and none of them appear to have been drilled out. I feel the car is driveable now, but I have read that these cars are supposed to shift more firmly than other cars and I worry that soft shifts are bad for my tranny in the long run. Should I adjust my vacuum control valve again to make sure I got it right or look for something else? I will send some test drive data on my vacuum now that I have adjusted the vcv. Thank you for the help! P.S.- what did I do when I turned that little screw on my vac amplifier fully clockwise? It seemed to reduce the vac output to the tranny. Is that where the screw should be or am I compensating for some other problem (too much vacuum from the vcv?) by doing that?

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87 300D 162,000 miles: It's not just a car, it's an adventure!

Your vacuum at idle is still too high. See what the vacuum at idle is when measured at the output from the VCV. To get mine down to 9", I had to adjust the VCV fully clockwise to the very end of it's travel. The vehicle has acceptable shifts........certainly not "firm". I haven't figured how to get that vacuum lower than 9"..........I'd prefer if it started at 8" or so.

The screw on the bottom of the amplifer adjusts the output to the trans.......effectively shifts the vacuum curve to the left or to the right........the unit can provide more vacuum to the trans than what the VCV shows, if adjusted counter-clockwise. When fully clockwise, I believe that it provides the VCV vacuum level until the boost comes on.

I finally got mine to shift right today. What you need to do is get under the car, and look for a little rubber cap on the drivers side of the transmission (it's not easy to see, it's really up high). Pull it off, then pull out the silver T handle and turn it a couple of times clockwise. Origianlly I had turned mine only about 1/2 a turn, but today I gave it a couple of turns and it really make the shift firm up. Still haven't hooked up a gauge to check the vacuum, but that's one thing I have to add to my list of things to do. I also turned the bowden cable one more time, and that helped to increase the time between the shifts.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

Thanks for the help, Brian. I will try readjusting the vcv and report back to you. When I measured vac at the vcv output before I started tweaking things, I got about 10.5 inHg at the vcv, so I guess the vac amplifier is still pushing the vac up. I think I turned it in the right direction b/c I think I was teed in after the vac amplifier at its output to the tranny and watched the vac go down as i turned the plastic screw. Maybe I need to double check and depending on my findings replace the vac amplifier? I will report back. Thanks again!

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87 300D 162,000 miles: It's not just a car, it's an adventure!

Ok, I turned my vcv fully clockwise and did a road test teed into the output of the vac amplifier. Shifts firmed up a little and no revving at 2-3 shift, but I think they may still be a bit soft and i still think I may have too much vac. At idle of 750 rpm I read 13 inHg. Under light pedal about 11inHg, under moderate pedal about 6 inHg, under heavy pedal O inHg. When I check vac with the same adjustments but teed into the output of the vcv I get 10 inHg at idle, 3 inHg under light pedal, 0 inHg under mod pedal, +1 under heavy pedal. I double checked to make sure I turned the plastic screw on the vac amplifier fully clockwise and indeed I did, I checked it while teed in and it is set at the minimum vac boost. Does this mean my vac amplifier is no good b/c it boosts my vac too much? I can get the vcv to give me very low to no vac under acceleration as reported above. If the vcv is ok, maybe one of the other inputs to the vac amplifier is the problem rather than the vac amplifier itself? What if I hooked something up wrong when I replaced my vac lines to the vcv? I will have to study a vac diagram and see if it matches what's under my hood. Everything was fine until I messed with my vac lines, so maybe I just hooked something up wrong.

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87 300D 162,000 miles: It's not just a car, it's an adventure!

studied my vac diagram, and my lines are hooked up corectly. now what?

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87 300D 162,000 miles: It's not just a car, it's an adventure!

From what I can tell from reading your posts, you still have not adjusted the modulator on the transmission. Read my above post, and try adjusting the modulator and see if that helps.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

RamJensen... where did you get your diagram?

Sam