Where is this thing? Is it the end of the brownish colored vac line that goes where eyes can't see? Is this something that is easy to access? Under the hood? Under the car?

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1989 300E 144K

Anyone?

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1989 300E 144K

It's located on the side of the tranny, under the car. This is a photo of one:

http://www.mercedesdismantlers.com/722.3and722.416_transmission_adjustments#722.3%20Series%20and%20722.416%20Transmission%20Adjustments

Just follow the vacuum line.

Mines 80 300SD, is located on the passenger side.
U need to jack it up or drive her on ramps.
make sure u block it well too. Or else u'll be as thin as a piece of Pizza.

I crawled in from right side.
When u see a vac line.
remove it, and u need to squeeze the metal clip with 2 pieces sticking out, then u can pop the cap out, the key should be in view. looks like a blank key that has never been cut. I turned mines up 2 notches. The shifting become much harsher. But it shifts better.
I also did the kick down linkage, it became bushing on the linkage more , result when step on gas the gear will hold longer. Sometimes it can stay up to 4000 RPM before she shifts.
The first to 2nd was the hardest, it kind of release with a bang. Can give mild whip lash!