I was under my 190E today trying to clear out the AC condensation drains and noticed the transmission modulator on the passenger side of the transmission was not connected to vacuum. The vacuum elbow was still there but not the feed line. I'm going to look for the line that's supposed tor run down there but what sort of issues could be caused by this missing line?

My transmission is very responsive but on the 1-2 and 2-3 up shifts, it can shift rather hard. This is a gas engine, and the engine doesn't seem to run quite as smoothly as it should even though I have done a bit of CIS and ignition work.

Could those be caused by this missing line?

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.

On transmissions in general, the vacuum modulator controls line pressure so no vac = high line pressure = hard shift. Vacuum tracks engine load.

On a trans with a cable running to the throttle, the shift points will be normal. On a trans without a cable ( there might be one for kick down however ) no vac = late hard shifts.

The trans will make shifts that'll break your neck.

The rough running could be due to the loose modulator line leaking vacuum. Investigate further.

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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When I accidently disconnected the Vac Hose to the Trans Modulator on mine the up shifts were nearly normal but the down shifts were jarring and harsh.

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84 300D, 82 Volvo 244Gl Diesel

Diesel911. That is exactly the way our diesels are engineered:

no vac = smooth upshift but clunky downshift
vac = smooth downshift