What's this hose for? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**TKCR** · 08-02-2015, 04:35 PM

I was replacing some dried out hoses today. When I replaced the bottom one and attached it to the hard line, the hard line felt like I knocked it loose. I got under the truck to see where this line went. It's not attached to anything, it's just an open end. Is it just a vent or something?
These 2 hoses are coming off the back of the intake manifold directly behind the carb. The bottom one goes down the firewall and underneath the chassis.

86 Chevy Silverado 2WD 305

**TKCR** · 08-02-2015, 04:38 PM

Here's the end that's under the truck

77 Big 10 · 08-02-2015, 05:32 PM

The only vacuum hard line that I can think of that goes under the truck in the vacuum line for the modulator for the trans. It will be on the passenger side of the trans, you should be able to see it from a rear view of the trans. It will be a small vacuum solenoid, like a round canister, with a nipple coming out of it. The hardline hooks to it with a piece of rubber hose.

**TKCR** · 08-02-2015, 06:04 PM

Quote:

Originally Posted by 77 Big 10

The only vacuum hard line that I can think of that goes under the truck in the vacuum line for the modulator for the trans. It will be on the passenger side of the trans, you should be able to see it from a rear view of the trans. It will be a small vacuum solenoid, like a round canister, with a nipple coming out of it. The hardline hooks to it with a piece of rubber hose.

I will get under there again and look for the solenoid. What is this solenoid for?

It is currently on the passenger side, just not connected to anything.

**TKCR** · 08-02-2015, 06:18 PM

I believe this is what you are talking about, and you can see the hard line next to it, unconnected. Also I found a coupler not hooked up, right above the solenoid, what's that and where does it go?

77 Big 10 · 08-02-2015, 06:34 PM

Could be for a th350 with a converter lock up. If you do not see a plug for it to plug into, it could be they changed the trans. The modulator helps the trans to shift. Just make sure the line is not leaking. Gook luck.

**TKCR** · 08-02-2015, 06:45 PM

Thanks for your help. And I was wondering about the trans being changed out, cause I actually found a couple more couplers not hooked to anything, and I couldn't find the other connection where they would go.
Again, thanks for the help!

77 Big 10 · 08-02-2015, 06:56 PM

No worries.

geezer#99 · 08-02-2015, 07:24 PM

When you get it hooked back up it should change how your truck shifts.
If not it is adjustable with that little screw inside. Turn it in cw if you want it to shift later. Turn it ccw for sooner shifts. Be aggressive in your adjustments. Try 3 turns at a time between tests.

08-02-2015, 04:35 PM	#1
TKCR Senior Member Join Date: Oct 2014 Location: Ohio Posts: 6,980	What's this hose for? I was replacing some dried out hoses today. When I replaced the bottom one and attached it to the hard line, the hard line felt like I knocked it loose. I got under the truck to see where this line went. It's not attached to anything, it's just an open end. Is it just a vent or something? These 2 hoses are coming off the back of the intake manifold directly behind the carb. The bottom one goes down the firewall and underneath the chassis. 86 Chevy Silverado 2WD 305 Attached Images

08-02-2015, 04:38 PM	#2
TKCR Senior Member Join Date: Oct 2014 Location: Ohio Posts: 6,980	Re: What's this hose for? Here's the end that's under the truck Attached Images

08-02-2015, 05:32 PM	#3
77 Big 10 Registered User Join Date: Jul 2015 Location: La Quinta, CA. Posts: 131	Re: What's this hose for? The only vacuum hard line that I can think of that goes under the truck in the vacuum line for the modulator for the trans. It will be on the passenger side of the trans, you should be able to see it from a rear view of the trans. It will be a small vacuum solenoid, like a round canister, with a nipple coming out of it. The hardline hooks to it with a piece of rubber hose.

08-02-2015, 06:18 PM	#5
TKCR Senior Member Join Date: Oct 2014 Location: Ohio Posts: 6,980	Re: What's this hose for? I believe this is what you are talking about, and you can see the hard line next to it, unconnected. Also I found a coupler not hooked up, right above the solenoid, what's that and where does it go? Attached Images

08-02-2015, 06:34 PM	#6
77 Big 10 Registered User Join Date: Jul 2015 Location: La Quinta, CA. Posts: 131	Re: What's this hose for? Could be for a th350 with a converter lock up. If you do not see a plug for it to plug into, it could be they changed the trans. The modulator helps the trans to shift. Just make sure the line is not leaking. Gook luck.

08-02-2015, 06:45 PM	#7
TKCR Senior Member Join Date: Oct 2014 Location: Ohio Posts: 6,980	Re: What's this hose for? Thanks for your help. And I was wondering about the trans being changed out, cause I actually found a couple more couplers not hooked to anything, and I couldn't find the other connection where they would go. Again, thanks for the help!

08-02-2015, 06:56 PM	#8
77 Big 10 Registered User Join Date: Jul 2015 Location: La Quinta, CA. Posts: 131	Re: What's this hose for? No worries.

08-02-2015, 07:24 PM	#9
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,736	Re: What's this hose for? When you get it hooked back up it should change how your truck shifts. If not it is adjustable with that little screw inside. Turn it in cw if you want it to shift later. Turn it ccw for sooner shifts. Be aggressive in your adjustments. Try 3 turns at a time between tests.



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