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marquis 12-31-2013 06:06 PM

Unknown line
 
1 Attachment(s)
Trying to figure out what this line is. The guy that had the truck before had it run into a pcv valve that connects to the manifold but didn't have the valve connected to the carb. It runs to the back of my transmission. Can anyone help me out?

tlawre87 12-31-2013 06:09 PM

Re: Unknown line
 
Its the vacuum modulator for the th350. It has to be hooked up for proper shifting. It should connect to the intake manifold.

marquis 12-31-2013 09:24 PM

Re: Unknown line
 
The valve that it connects to has two ports. I'm assuming that I should keep the second one plugged and not connected to the carb?

cory d 12-31-2013 09:53 PM

Re: Unknown line
 
thats the vacuum modulator valve on a th350. it helps control your shift points with your vacuum. shift earlier when just cruising of holds the gear long when wide open. if its not connected at all you will just shift off of the governer. if i recall correctly, i havent ran an automatic in a while

buddy_1 12-31-2013 11:09 PM

Re: Unknown line
 
That modulator in the pic looks like it is leaking fluid probably needs to be replaced. Got a pick of the valve that it connects to? The reason I ask is that you said it has 2 ports and the modulator needs vacuum to work correctly. If that valve isn't connected to the carb/intake that second port needs a hose hooked to a vacuum source.

marquis 12-31-2013 11:31 PM

Re: Unknown line
 
1 Attachment(s)
Yea I have to go over my transmission with a fine tooth comb because it think there's more than one leak. So I do need to hook the other port up to the carb?

875.3CHEVY 12-31-2013 11:42 PM

Re: Unknown line
 
no thats hooked up right.straight vaccum off the monifold

marquis 01-01-2014 12:09 AM

Re: Unknown line
 
The pcv valve port being used is the one that goes to the transmission not the carb.

buddy_1 01-01-2014 12:23 AM

Re: Unknown line
 
I agree with 875.3, it is connected correctly. To help prevent the vacuum hose from collapsing, the nipple on the pipe is supposed to fit directly into the fitting on the intake with a hose over the union.

875.3CHEVY 01-01-2014 12:46 AM

Re: Unknown line
 
the fitting behind the carb with the orange line and the capped off port is not a pvc port.it just straight vaccum.that what the trans needs.pvc should come off the carb and should be 3/8 in size.hope this helps

marquis 01-01-2014 01:38 AM

Re: Unknown line
 
Thank you guys very much. I was very confused haha.


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