Transmission modulator / vacuum pipe TH400
11-24-2010, 06:16 PM
#1
Racer
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Transmission modulator / vacuum pipe TH400
'73 350, 400TH
A couple of questions:
1) what is the purpose of the vacuum modulator of the TH400 Transmission?
(I was thinking either it is the controller for downshifting or the controller for normal shifting?)
2) I bought a repro modulator-to-intake steel line. It is supposed to have a "restriction". It doesn't. How's about I make a restriction - fill one end with acid core solder and drill out 1/8 hole. Would that be close?
(I can't find a real pipe to see what the actual restriction is)
thanks!
A couple of questions:
1) what is the purpose of the vacuum modulator of the TH400 Transmission?
(I was thinking either it is the controller for downshifting or the controller for normal shifting?)
2) I bought a repro modulator-to-intake steel line. It is supposed to have a "restriction". It doesn't. How's about I make a restriction - fill one end with acid core solder and drill out 1/8 hole. Would that be close?
(I can't find a real pipe to see what the actual restriction is)
thanks!
11-24-2010, 06:52 PM
#2
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I wouldn't worry 'bout constricting the tube; vacuum is vacuum. What the modulator does is tell the transmission how deep your foot is into the gas, so that it knows how long to delay the shift.
A turbo 400 has no detent cable, so the modulator is pretty important. At WOT, the downshift signal is sent electrically from a switch that closes when you mash the pedal. It signals the trans to downshift, as long as it's within RPM limits.
A turbo 400 has no detent cable, so the modulator is pretty important. At WOT, the downshift signal is sent electrically from a switch that closes when you mash the pedal. It signals the trans to downshift, as long as it's within RPM limits.
11-24-2010, 07:04 PM
#4
I do not know of any restriction but the tube is reduced in size on the end so it will fit into the end of the modulator. A short piece of hose then makes the seal. mike...
Just noticed my upper cooler line is leaking. Oh well, I needed something to do this weekend.
Just noticed my upper cooler line is leaking. Oh well, I needed something to do this weekend.
Last edited by mds3013; 11-24-2010 at 07:25 PM.
11-27-2010, 09:38 AM
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