How much do these little vacuum orfice have an effect on the transmission?

[Lenovolost]

https://**************.com/store/diesel-automatic-shift-control-valve-vacuum-orifice-set

84 300D. Overhauled the vacuum line/hoses/3 way t's in my car and realized I accidentally threw away these orfices. My car is shifting a little rough. Vacuum is good car shuts off on the dim. I will do a little more digging in the AM. However I just wanted to know do they play a big role in how the transmission works?

[H-townbenzoboy]

Originally Posted by Lenovolost

https://**************.com/store/diesel-automatic-shift-control-valve-vacuum-orifice-set

84 300D. Overhauled the vacuum line/hoses/3 way t's in my car and realized I accidentally threw away these orfices. My car is shifting a little rough. Vacuum is good car shuts off on the dim. I will do a little more digging in the AM. However I just wanted to know do they play a big role in how the transmission works?

See this post It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ...

I got rid of the orifice when I streamlined my vacuum lines after eliminating the EGR and the associated valves on top of the valve cover of my 1981 300SD. After I saw a photo of the engine of a rare Japanese spec 300SD that came from the factory without the EGR, I noticed the vacuum line didn't have an orifice. The EPC confirmed it for non-EGR 300SDs, so I removed it. My transmission shifts well without the orifice.

Your car may be different. I think later models used more orifices, so eliminating them may result in more dramatic changes to shifting to your 1984 model. How many did you remove?

[Lenovolost]

Originally Posted by H-townbenzoboy

See this post It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ...

I got rid of the orifice when I streamlined my vacuum lines after eliminating the EGR and the associated valves on top of the valve cover of my 1981 300SD. After I saw a photo of the engine of a rare Japanese spec 300SD that came from the factory without the EGR, I noticed the vacuum line didn't have an orifice. The EPC confirmed it for non-EGR 300SDs, so I removed it. My transmission shifts well without the orifice.

Your car may be different. I think later models used more orifices, so eliminating them may result in more dramatic changes to shifting to your 1984 model. How many did you remove?

basically all three of them. My vacuum system is very simple after disabling EGR/AC/Doorlockz

[ykobayashi]

They make a big difference on shift firmness on my 85 300d. I ripped out my egr to get rid of leaks. Also got rid of the vacuum amplifier among other odds and ends. When I was all done I adjusted the firmness of my shift by adjusting a single orifice size on one of the transmission control lines...it was either a bleed off or the line to the modulator or VCV. I cannot recall. The end result was I could increase or decrease the vacuum seen by the transmission modulator. I did this on previous cars using the adjustment screw in the VCV but I decided to try with the handful of leftover orifices after the egr delete.

[Dankly1]

Does anyone have any extra orifices sitting around their shop? A PO removed them and I am having a heck of a time getting my 85 300TD to shift properly.

Thanks!
Alex

[Lenovolost]

Originally Posted by Dankly1

Does anyone have any extra orifices sitting around their shop? A PO removed them and I am having a heck of a time getting my 85 300TD to shift properly.

Thanks!
Alex

Me and you both I've locked deep online no one sells them except Kent but for an outrageous price. I wonder if if their is an alternative?

[ykobayashi]

You make them.

Get some small circuit board drills and bore out some plastic rod with different diameters and put it inline in the hose.

Or, find some tubing, fill it with hot glue and use little wires and pins of varying diameter and poke holes after heating the pins with a lighter.

Be creative.

[Alec300SD]

Originally Posted by Lenovolost

Me and you both I've locked deep online no one sells them except Kent but for an outrageous price. I wonder if if their is an alternative?

On my 83 300SD I replaced the white restricted orifice connector with a drip irrigation needle valve from OSH.

This allowed me to 'dial-in" the restricted orifice size that was just right to obtain the downshift quality I wanted.

[ykobayashi]

That’s brilliant

[BillGrissom]

Think of it like an electrical circuit. I assume the way it works is that the VCV is like a variable resistor (rheostat) in series with a fixed resistor (orifice). That forms a "voltage-divider" which gives a "voltage" (vacuum pressure) signal to the transmission's vacuum modulator. Without the orifice, the transmission would get the full upstream vacuum (voltage source), less pressure drops from flow in the tubing. In 1985 cars, the "Blue Saucer" is a vacuum "buffer amplifier" between the VCV signal and transmission. Probably a good idea since they continued that 1986+, and why I put one in my 1984 300D (mounting holes were already there). The adjustable orifice by Alec300SD sounds good, if you spend the time to tweak it.

For those who don't know, the whole purpose of the VCV circuit is to simulate the normal intake vacuum signal of a gasoline engine. It works based on fuel pedal position. A bit clumsy, but the easiest way M-B could adapt these mechanical transmissions to a diesel engine. If Chrysler were doing it, they wouldn't need this since their Torqueflite transmissions get no vacuum signal from the gas engine. Ditto for GM I think. Seems old Ford transmissions had a similar vacuum signal since you see what appears to be a large vacuum piston on the side of their case, similar to the B-2 piston in the M-B transmissions.