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Old 01-09-2012, 03:33 PM   #1
Hazieview
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th350 Transmission Vacuum line to intake???

Hey does the vaccum line from a th350 transmission hook to your intake? (At least I think it is called a vacuum line )

Do I need to run a hose from the gold looking thing with the green square to the hole on my intake with the red circle?




Not a trani guy at all. Just need to know if I need to hook that thng there to dilly flop over yonder...? I dont want to put the square block in the round hole if you know what I mean
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Old 01-09-2012, 03:40 PM   #2
beamn7
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Re: th350 Transmission Vacuum line to intake???

Yes, you are correct. The "gold looking thing" is the Vaccum Modulator....
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Old 01-09-2012, 03:41 PM   #3
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Re: th350 Transmission Vacuum line to intake???

That will work! Thats the way mine is hooked up.
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Old 01-09-2012, 03:47 PM   #4
Hazieview
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Re: th350 Transmission Vacuum line to intake???

Thanks guys, any idea what size hose I need? Everything I have is pretty much braided stainless steel. So if I could find the right size hose in braided stainless steel that would be great!

Will one of these work?
http://www.summitracing.com/parts/SPE-7839/

It is 3/8" or would the 5/32 be better?

thanks again!
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Last edited by Hazieview; 01-09-2012 at 03:56 PM.
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Old 01-09-2012, 04:47 PM   #5
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Re: th350 Transmission Vacuum line to intake???

Same size as the modulator on the trani. I would not go smaller ID size. I have used different size ID hose and had no changes as long as ya get it sealed up with no vacuum leaks!

I like to bend solid line and use a short hose at each connection. Vacuum can suck a line closed causing fast shifts & other problems.......Just my 2 cents worth.
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Old 09-05-2012, 10:26 AM   #6
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Re: th350 Transmission Vacuum line to intake???

i just want to say this thread is awesome and exactly what I was looking for. thanks for putting it in "lame" man terms Hazie, I needed that to understand what I was looking at!! LOL
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Old 01-17-2016, 06:34 PM   #7
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Re: th350 Transmission Vacuum line to intake???

What does the vacuum modulator thingy do?
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Old 01-17-2016, 06:47 PM   #8
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Re: th350 Transmission Vacuum line to intake???

The vacuum modulator, together with the governor, controls the shift points on the TH350 transmission. All stock TH350s were manufactured the same; their differences in shift characteristics for specific engines and vehicles were set with the governor and modulator.

The governor lives behind a cap secured by a bail on the drivers side of the transmission in front of the tail cone. It is a little widget that spins with the output shaft. There are flyweights and springs on this spinning widget, and when the flyweights overcome the springs and hydraulic pressure, the flyweights push open a rod valve that lives in the center of the governor shaft. Adjusting the governor weights and springs can be done to adjust the wide-open throttle shift points of the transmission.

The vacuum modulator adjusts the hydraulic pressure to the governor dependent on the engine vacuum. At wide-open throttle (low vacuum), the full hydraulic pressure is provided to the governor and the wide-open throttle shift points are selected. When there is engine vacuum on the modulator, the hydraulic pressure to the governor is reduced, and the governor finds it easier to overcome the hydraulic pressure to open the shift valve, so earlier shifts are selected. Adjustment or replacement of the vacuum modulator can be used to adjust the part-throttle shift points.

The kick-down cable on the TH350 bypasses the modulator and provide full pressure to the governor, enabling the wide-open throttle shift points. The result is that, when the pedal is depressed past the kick-down point, the modulator is bypassed, and the full hydraulic pressure provided to the governor, which will cause the transmission to downshift if it is below the RPM for the wide-open throttle shift point.

Does that help?
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Old 01-17-2016, 06:53 PM   #9
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Re: th350 Transmission Vacuum line to intake???

That really helps a lot.
Thanks
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Old 01-17-2016, 07:15 PM   #10
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Re: th350 Transmission Vacuum line to intake???

Found a pic of the metal line routing.
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Old 01-18-2016, 07:58 PM   #11
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Re: th350 Transmission Vacuum line to intake???

Looks like the metal line is around 36". The rest is made up with the hose.
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Old 10-11-2017, 02:58 PM   #12
CHEVYNEVERDIE
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Re: th350 Transmission Vacuum line to intake???

where can I find transmission vacuum line for my 1977 Chevrolet c10 automatic? I tried ebay and all it shows Camaro, el camino and those are not the same even classicparts, brothers, industrial classic ...
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Old 10-11-2017, 03:05 PM   #13
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Re: th350 Transmission Vacuum line to intake???

Quote:
Originally Posted by CHEVYNEVERDIE View Post
where can I find transmission vacuum line for my 1977 Chevrolet c10 automatic? I tried ebay and all it shows Camaro, el camino and those are not the same even classicparts, brothers, industrial classic ...
I just made my own out of a pre-made flexable brake line piece I bought down at Autozone.
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