Thread: '79 454 transmission vacuum line?

Tweet

I pulled a 79 suburban 454 and put it into my nova. As stock, it had a vacuum line coming from the transmission up to the intake menifold and was hooked up to some soprt of source there. Since I have just replaced the intake and carb (no longer have any vacuum source, dominator carb) the transmission wont shift gears unless i nearly floor it and get higher up in the rpm range.

Could this have something to do with that vacuum line, and what is it anyway? I checked the tranny fluid and filled it, same problem. No idea!

Originally posted by ericingram

Could this have something to do with that vacuum line, and what is it anyway?

Yup. Vacuum line goes to the Modulator valve... tells the trans. when to shift.

Originally posted by ericingram

Could this have something to do with that vacuum line, and what is it anyway?

Yup. Vacuum line goes to the Modulator valve... tells the trans. when to shift.

Great, at last i've found the problem, is there any way to fix or disable this other than getting a new carb or trans? ;p

Originally posted by ericingram
Great, at last i've found the problem, is there any way to fix or disable this other than getting a new carb or trans? ;p

Go to this web site. It might answer some questions. If you scroll down the page you will find this vacuum less modulator. I would try to find a place to pick up vacuum and make the modulator you have now work. How about a carb. adapter plate with a vacuum coupler?

http://www.400raptor.com/

This modulator is a little spendy. Finding vacuum source would be cheaper. Maybe somebody else has an idea I'm not thinking of.

Tee into your power brake booster supply, if ya ain't running one put a fitting to where it would go at the back of the intake and if one aint there, drill and tap one.

I think im going to get a 2" carb spacer and tab that for a fitting.

Thanks for the help!