Adjust tranny modulator?

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Henry - 24 Sep 2005 21:09 GMT

I have an old Chevy pickup with 454 engine and 3 speed THM400.

I just put a new tranny modulator in it as old one leaked and allowed
tranny fluid to get past diaphragm.

New one is Fram FM2321, with green stripe, same as my old one. It is
adjustable, as was the old one. Does anyone know which way to turn the
screw, and what to look for?

Regards,

Henry

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Shep - 24 Sep 2005 21:24 GMT

Lessening the vacuum will increase and firm up the shifts, kind of a seat of
the pants deal here.

>I have an old Chevy pickup with 454 engine and 3 speed THM400.
>
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> Henry

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John Kunkel - 24 Sep 2005 21:36 GMT

>I have an old Chevy pickup with 454 engine and 3 speed THM400.
>
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> adjustable, as was the old one. Does anyone know which way to turn the
> screw, and what to look for?

Turning the screw clockwise will raise the part throttle shift points.

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Henry - 24 Sep 2005 23:11 GMT

THANK YOU for the info. I couldn't find it anywhere on the 'net.

Henry

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lugnut - 25 Sep 2005 15:47 GMT

>I have an old Chevy pickup with 454 engine and 3 speed THM400.
>
[quoted text clipped - 8 lines]
>
>Henry

It turns clockwise to raise the shift points -
counterclockwise to lower the shift point. I usually try to
set it where the 1-2 shift occurs at 8-10 mph at minimum
acceleration on level ground. The modulator controls the
1-2 shift. If you set it too high, you will get a delayed
or hang shift under load. This is a seat of the pants
adjustment to some extent. You will know when you get it
right. You should adjust it in about 1/8 turns at a time
once you get it in the ballpark.

Lugnut

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