hard shift into second on heavy acceleration.
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From: Virginia
So the tranny problem is a violent shake when it shifts from 1 to 2? And it only does it when it's floored? It shifts fine otherwise?
The modulator valve is located on the rear pass side of the trans. It has a small vacuum line going to it. Usually if it goes bad the tranny will refuse to shift at all until the engine winds way up, 1-2 and 2-3 shifts. Another failure mode is the diaphragm in the modulator will get a hole in it and the engine vacuum will suck trans fluid up into the engine. The engine will smoke terribly when this happens, besides not shifting correctly also.
The modulator valve is located on the rear pass side of the trans. It has a small vacuum line going to it. Usually if it goes bad the tranny will refuse to shift at all until the engine winds way up, 1-2 and 2-3 shifts. Another failure mode is the diaphragm in the modulator will get a hole in it and the engine vacuum will suck trans fluid up into the engine. The engine will smoke terribly when this happens, besides not shifting correctly also.
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Joined: Feb 2008
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From: St Albert, Alberta
Since you have changed the fluids already drain a couple of liters of the Dexron and add Type F in it;s place.
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So the tranny problem is a violent shake when it shifts from 1 to 2? And it only does it when it's floored? It shifts fine otherwise?
The modulator valve is located on the rear pass side of the trans. It has a small vacuum line going to it. Usually if it goes bad the tranny will refuse to shift at all until the engine winds way up, 1-2 and 2-3 shifts. Another failure mode is the diaphragm in the modulator will get a hole in it and the engine vacuum will suck trans fluid up into the engine. The engine will smoke terribly when this happens, besides not shifting correctly also.
The modulator valve is located on the rear pass side of the trans. It has a small vacuum line going to it. Usually if it goes bad the tranny will refuse to shift at all until the engine winds way up, 1-2 and 2-3 shifts. Another failure mode is the diaphragm in the modulator will get a hole in it and the engine vacuum will suck trans fluid up into the engine. The engine will smoke terribly when this happens, besides not shifting correctly also.
also it didn't have a vacuum line at all connected to the modulator so I added one but haven had the chance to test it out yet, i'll update tomorrow after I get the chance to drive it.
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alchemist1
1973 - 1979 F-100 & Larger F-Series Trucks
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Mar 25, 2013 11:55 AM
