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12-14-2004, 12:46 AM | #1 |
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Join Date: Jun 2004
Location: Beeville, Texas
Posts: 1,943
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TH400 trans vacuum modulators
A couple weeks ago I replaced the old, huge vacuum modulator on the TH400 in my truck and now it shifts really fast, I'm talking 1st to 2nd at like right below 10MPH. The old style ones have been discontinued and the replacements are friggin small, like 1/3 the size of the old ones. The bad thing is the shift points on these aren't adjustable, they don't have the screw sticking out of the end. Can the old style ones still be bought somewhere even though they're discontinued? Every dam* place I checked at only has the stupid small ones. The tranny is a '67 out of a Chevy Caprice if that matters.
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RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck |
12-14-2004, 01:00 AM | #2 |
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Join Date: Apr 2000
Location: Delta,Pa
Posts: 14,950
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the screw doesnt stick out the end of the modulator its inside the nipple you need a small screwdriver to turn it in.
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Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member. |
12-14-2004, 11:36 AM | #3 |
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Join Date: Jul 2001
Location: Muskegon,MI,USA
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If your modulator does not have the little screw in the nipple, then you can install a valve in the vacuum line to adjust the shift point. Here is a pic of what has been done to adjust the vacuum.
Jim |
12-14-2004, 11:10 PM | #4 |
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Location: Beeville, Texas
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Jim I've never seen a valve like that before, where'd you get that? At least it goes to third when I'm on the highway, that's all that matters right now. I did manage to find an old NOS one in my Granddad's garage, at least I'll have an original one when I need it. Thanks for the help cableguy, I'll check if I have a screwdriver small enough and I'll try and see if I can adjust it sometime this week.
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RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck |
12-15-2004, 12:02 AM | #5 |
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Join Date: Aug 2001
Location: Castlegar B.C. Canada
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hmm technically you could use any valve for that line, even something from a fish tank would work, just needs to adjust the amount of vacum going to the tranny
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12-15-2004, 08:30 AM | #6 |
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Join Date: Jul 2001
Location: Muskegon,MI,USA
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Robert,
Hooter is right just about any valve will work. The nice features of the valve shown is that it is small, well made, and it has a locking feature on it. There are several manufacturers of these small valves. They are available at industrial supply stores as they are used for controlling pneumatic cylinders in air assembly machines among other uses. If you need any other information on them I will be glad to get it for you. Jim |
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