where on the trans is the modulator located

I am in the process of fixing my vacuum system and next on the list is the modulator

Thanks

1984 300d

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Ok I just came from "underneath the car" and I adjusted the modulator. When I shift at 1500 RPM it doesn't "clunk" anymore, and when I give it more throttle it doesn't do a burnout when it shifts into 2nd gear. Turns out the modulator is green instead of black, even though I thought the california ones are black.
When you have a modulator with the T handle on top and keep turning it left, is there a stop? Mine just becomes really loose after the adjustment stage. Is that supposed to happen? Or is there something inside it not "following" the adjustment?

hi, reviving this thread b/c i have a modulator from a donor transmission that got me out of first gear...

the car's a 1980 300d (non-turbo) and had the red vacuum modulator (trans # 722.118). i couldn't get out of first/second gear, but when i put in a white vacuum modulator from a 1979 300sd (trans # 722.120) i got all of my gears back, but am having trouble adjusting shift points.

my questions are:
1) will this white modulator work--does anyone have successful experience?
2) would my original red modulator be serviceable?

(oops, should i move this to diesel discussion??)
thanks a bunch!
-noah

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1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)