Transmission Vacuum?

[Hooker]

Where does the transmission (th350 i think) vacuum line go to on a holley street avenger carb? Does it draw full vacuum?

[bad72c10]

I ran mine to manifold vaccuum while I still had it, so I'd say it does pull full vaccuum. You may be running your brake vaccum back just behind the carb on the manifold, and if you are, thats exactly where my vaccuum line to the modulator on the tranny went to. Justin

[Billla]

Vacuum modulator should connect to manifold vacuum - either from unported vacuum on the carb or a fitting directly on the manifold.

[Hooker]

what does the modulator do anyway?

[VetteVet]

Originally Posted by Hooker

what does the modulator do anyway?

you had to ask.
http://yarchive.net/car/transmission.html

[bad72c10]

I know it cushions shifts, not sure about anything else. Justin

[jhow66]

Originally Posted by Hooker

what does the modulator do anyway?

Shifts trans at part throttle and smooths the shifts. Governor controls shifts at full throttle. To see what I am talking about, take the vacumn line off (plug both ends) and shift trans into a gear. It will be a big thump. Also if modulator is bad, it will not shift into high gear at part tthrottle until you let off the gas. (the above advice comes with no warrenty implied or otherwise )

[el3m3nt3l]

is it possible to draw trans fluid into the intake from the vacuum line?

[MagmaJct]

My understanding of an automatic transmission is that both the governor AND the modulator control when the transmission shifts and into which gear. Just think of how you control a manual transmission.

Higher speeds require higher gears, however, higher loads require lower gears.

If I'm missing anything, I'm sure others will chime in. But I don't think the modulators job is to simply smooth shifts, I just think without it the transmission isn't getting all the information needed to do it's job correctly.

[Tx Firefighter]

Originally Posted by el3m3nt3l

is it possible to draw trans fluid into the intake from the vacuum line?

Yes, if the diaphram inside the modulator is leaking, it will allow engine vacuum to draw fluid out through the line and into the engine where it gets burned. A new modulator will fix this.

[el3m3nt3l]

Originally Posted by Tx Firefighter

Yes, if the diaphram inside the modulator is leaking, it will allow engine vacuum to draw fluid out through the line and into the engine where it gets burned. A new modulator will fix this.

just as i suspected. thanks for the info.

[406 Q-ship]

Originally Posted by Tx Firefighter

Yes, if the diaphram inside the modulator is leaking, it will allow engine vacuum to draw fluid out through the line and into the engine where it gets burned. A new modulator will fix this.

The smoke is white in color (like water) but smells different. The Transmission will shift late and harder when the line is disconnected or the modulator has failed.

Goes to manifold vacuum always.