vacuum system problem

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Jan 23, 2017 | 11:46 AM

forango

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Tuned

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vacuum system problem

I was curious if the power braking system has any influence on the vacuum system in these trucks?

I have been dealing with a problem in our truck(1978 F100 302 2bbl C6) for a while now where it comes out of gear at lower rpm's.

Yesterday i did a lot of work on it...changed out vacuum modulator to the green stripe version with the screw backed out a couple turns and lowered the idle speed(which was way high) as well as lubing the throttle linkage so it came all the way back to idle...these things helped touch but was still having the issue when would come to complete stop...while running down the road it operates perfectly.

So I experimented on my street and just put it in gear and let it roll at idle speed...it never kicked out of gear Until I applied the brakes to a full stop...release the brake and 5-7 seconds later it would go back into gear and start rolling again.

thoughts?

Jan 23, 2017 | 11:54 AM

forango

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The other reason i am asking about the braking is one of the vacuum lines runs up the firewall and appears as thought it somehow ties into the brake booster.

Jan 23, 2017 | 12:35 PM

meangreen92

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Does the engine rev like the transmission is in neutral, when it's doing this?

Jan 23, 2017 | 12:42 PM

forango

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Tuned

Joined: Feb 2016

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Quote:

Originally Posted by meangreen92

Does the engine rev like the transmission is in neutral, when it's doing this?

Yes....but while going down the road the transmission does not slip nor comes out of gear until you come to a stop again. or after a good brake application.