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Vacuum line on trans

K

Kats66Pny

Active Member
pretty sure I didn't connect it when I installed the tranny. I was trying to figure out where it goes and ran across info stating if you have a manual valve body, it's not needed?

I'm 99% sure I have a MVB since my B&M shifter only works in ratchet mode and has to be manually shifted. I was looking at 'before' pictures and there was a vacuum line coming from the trans, so I'm confused if I need it or not. :shrug
 
A C4 trans has a modulator ( rear right side ) thats connected with a vacuumline to the intake manifold.
When the car is under load ( read : no vacuum in manifold / trottle wide open ) , the lack of vacuum on/in the modulator will resilt in a downshift of the trans.
IIRC.
So please guys correct me if I am wrong.But thats what I always taught about it.
 
IMO
You can always shift manually , vacuumline connected or not.
But it CAN automatically downshift when you accelerate a bit harder , or do it by yourself by pulling the shift lever one notch.
But keep in mind , I am not an expert.
 
"blue65coupe" said:
Not if you're strictly manual shifting. Could it be you can only manual shift because it's not hooked up?
Click to expand...

At first we thought it was the shifter just not being properly hooked up, but it is. I even printed out the Quicksilver installation sheet. Either way, I like having to manually shift so doesn't bother me I can't use it in automatic mode.

I just don't want to hurt anything if there's no line when there needs to be one. :hide
 
"B67FSTB" said:
A C4 trans has a modulator ( rear right side ) thats connected with a vacuumline to the intake manifold.
When the car is under load ( read : no vacuum in manifold / trottle wide open ) , the lack of vacuum on/in the modulator will resilt in a downshift of the trans.
IIRC.
So please guys correct me if I am wrong.But thats what I always taught about it.
Click to expand...
that's right Bruno and Kat if it has a manual VB it wont need to be hooked up and it won't hurt anything. I don't think they will go into drive (3rd) if it is an automatic and the modulator isn't working or hooked up.
 
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