th400 vacuum modulator install
Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
th400 vacuum modulator install
i'm changing a munci to a th400 (yeah, don't yell at me). the aim shows the modulator vacuum inlet in a horizontal position. is that critical? also, when i removed the modulator originally it had two O rings on the pipe that inserts into the trans. i replaced them with one nitril O ring that seats on the lip of the pipe so that it is compressed when the modulator is installed. correct? or do the O rings belong on the pipe in such a way that the seal is formed between the pipe and the input tube(that's how the po had them installed)? also, when i push the modulator into the trans, the last 1/16" inch or so seems to have a spring loaded tension(not caused by the O ring). normal? it's been 45 years since i last installed a modulator and i can't remember.
by the way, i bought one of those vibrating cutting tools and used it to cut out the fiberglass in the footwell where it has to be modified-great invention! made easy work of what could have been a laborious job.
by the way, i bought one of those vibrating cutting tools and used it to cut out the fiberglass in the footwell where it has to be modified-great invention! made easy work of what could have been a laborious job.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
The AIM shows the modulator installed with the tube facing forward- so the steel line from the top and the pre-cut rubber ends will reach. No real reason other than that.
Some have used 2 o-rings, trying to prevent a leak. (maybe if one is good, two has to be better?) One is what is supposed to be there.
Under the modulator, in the case, is a valve. If it comes out, it has to go back in the same way- flip it over and it won't shift correctly, if at all. And the spring tension is correct. The last little bit, you're pushing the valve into the end of the modulator. SOme shift kits have a helper spring that goes on the end of the valve too.
Some have used 2 o-rings, trying to prevent a leak. (maybe if one is good, two has to be better?) One is what is supposed to be there.
Under the modulator, in the case, is a valve. If it comes out, it has to go back in the same way- flip it over and it won't shift correctly, if at all. And the spring tension is correct. The last little bit, you're pushing the valve into the end of the modulator. SOme shift kits have a helper spring that goes on the end of the valve too.
