My 83 300DT has always shifted harshly, especially when cold. I've replaced the transmission vacuum modulator and have been trying to set the pressure using the key on top of the modulator.

With the vacuum line disconnected, I am getting a reading of 3.8 bar, when it looks like it should be around 2.9 bar.

I've tried turning the key far enough out that it will not sit in the castellations on top of the modulator, but there seems to be a point where it does not affect the pressure and I can't get it below 3.8 bar.

Any ideas?

Thanks,
Tim Irwin

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Tim Irwin
1983 300D
1994 Miata R Package
unnamed family car