Vacuum modulator line question?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

newmaac · 11-04-2011, 12:19 AM

I am installing a TH350 in a 69 C-10 longbed with a 350 engine.
The truck originally had a 3 on the tree.

I don't have a modulator line for this transmission.
I assume that originally there was a pre-bent line, with rubber hose on the ends to attach to the manifold and modulator???

1. Am I correct in that assumption?
2. Can I simply run a length of 5/16" vacuum line to make this connection? With the modulator facing towards the rear, it seems like I would have to have a fair amount of slack in the line, in order not to kink it.
3. anyone have a spare line or a suggestion for a good source?

TIA,
Mike

**LockDoc** · 11-04-2011, 12:27 AM

Quote:

Originally Posted by newmaac

I am installing a TH350 in a 69 C-10 longbed with a 350 engine.
The truck originally had a 3 on the tree.

I don't have a modulator line for this transmission.
I assume that originally there was a pre-bent line, with rubber hose on the ends to attach to the manifold and modulator???

1. Am I correct in that assumption?

You are correct.

2. Can I simply run a length of 5/16" vacuum line to make this connection? With the modulator facing towards the rear, it seems like I would have to have a fair amount of slack in the line, in order not to kink it.

I wouldn't do that, I would run metal. There is a pre-bent rubber line that goes from the metal line to the modulator. It is formed in a "U" shape.

3. anyone have a spare line or a suggestion for a good source?

You could just use 3/16" or 1/4" brake line and buy the "U" shaped piece at NAPA or other automotive supply store...

TIA,
Mike

LockDoc

bigsnookmaster · 11-04-2011, 07:34 AM

I'd go to the local pick n pull and browse and see what they might have. It would probably be on some of the older cars.

hugger6933 · 11-04-2011, 07:37 AM

Rubber all the way might collapse easily and not get a good vacsignal. Of course that probably would'nt happen right away

MARKDTN · 11-04-2011, 07:42 AM

I have used DOT 1/4" plastic air line for this with a little rubber hose on each end. DOT air line is tough stuff.

newmaac · 11-04-2011, 10:53 AM

Thanks for the quick responses, folks.
We are running a piece of hose just for today, to take a test drive and assess everything.
Sometime this weekend I will get some tubing and bend a new one.
Thanks again,
Mike

11-04-2011, 12:19 AM	#1
newmaac Registered User Join Date: Jun 2011 Location: Cupertino, CA Posts: 17	Vacuum modulator line question?? I am installing a TH350 in a 69 C-10 longbed with a 350 engine. The truck originally had a 3 on the tree. I don't have a modulator line for this transmission. I assume that originally there was a pre-bent line, with rubber hose on the ends to attach to the manifold and modulator??? 1. Am I correct in that assumption? 2. Can I simply run a length of 5/16" vacuum line to make this connection? With the modulator facing towards the rear, it seems like I would have to have a fair amount of slack in the line, in order not to kink it. 3. anyone have a spare line or a suggestion for a good source? TIA, Mike

11-04-2011, 07:34 AM	#3
bigsnookmaster Registered User Join Date: Jan 2008 Location: St.Petersburg,Fl Posts: 1,267	Re: Vacuum modulator line question?? I'd go to the local pick n pull and browse and see what they might have. It would probably be on some of the older cars. __________________ greg http://community.webshots.com/user/68406Stepside

11-04-2011, 07:37 AM	#4
hugger6933 Registered User Join Date: Oct 2008 Location: Marianna Arkansas Posts: 7,280	Re: Vacuum modulator line question?? Rubber all the way might collapse easily and not get a good vacsignal. Of course that probably would'nt happen right away

11-04-2011, 07:42 AM	#5
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,165	Re: Vacuum modulator line question?? I have used DOT 1/4" plastic air line for this with a little rubber hose on each end. DOT air line is tough stuff. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

11-04-2011, 10:53 AM	#6
newmaac Registered User Join Date: Jun 2011 Location: Cupertino, CA Posts: 17	Re: Vacuum modulator line question?? Thanks for the quick responses, folks. We are running a piece of hose just for today, to take a test drive and assess everything. Sometime this weekend I will get some tubing and bend a new one. Thanks again, Mike



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