Transmission vac modulator

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Simon Dove
170s
Posts: 179
Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Transmission vac modulator

Post by Simon Dove » Sat 10 Mar, 2018 11:14 am

I purchased a new vac modulator for my W126 (722.324) a few weeks ago after my 420sel stated to get a hard downshift from 4 to 3 gear.
After reading the installation instructions it was recommended to set the operating pressure of the trans to 52psi (psi varies depending on model). Super cheap auto has an oil pressure kit with the appropriate adapter for about $35 (see photo)
After installing and adjusting pressure to 52 Psi there was a slight flare when shifting gears. I ended up using 57 psi to have a positive shift between gets without being to hard. The downshift from 4 to 3 is now silky smooth.
A fairly easy install and reasonably inexpensive fix which makes driving the ole girl a lot smoother :dance:
I disassembled the old modulator for reference.

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71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

User avatar
Simon Dove
170s
Posts: 179
Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Re: Transmission vac modulator

Post by Simon Dove » Sat 10 Mar, 2018 11:37 am

And the other two pics which didn't come through on the first post.
image.png
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71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

CraigB
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Joined: Thu 23 Jun, 2005 2:18 pm
Model you own: I own multiple different models
Location: Hawthorndene (Adelaide)

Re: Transmission vac modulator

Post by CraigB » Sat 10 Mar, 2018 6:09 pm

Thanks for sharing that info. Just had a quick look and I guess that is the toolpro kit. Where did you source the modulator from?

It still seems to not like your last pic.
Craig Baulderstone
Lurch
280s's
280SE3.5
280SL
350SL
500SEC's
560SEL's

User avatar
Simon Dove
170s
Posts: 179
Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Re: Transmission vac modulator

Post by Simon Dove » Sat 10 Mar, 2018 11:25 pm

I've just returned from a training course in the US. I bought the modulator and other bits from pelican parts.

And yes your right I've got pics to come but being challenged by technology :banghead: see if this works
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71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

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