C4 Vacuum Modulator Hose

[Tcb3078]

Just wrapping up my build. I did rubber hose the entire length of the vacuum modulator vs installing the metal piece. Any concerns with this?

 

[Viperwolf1]

No problem as long as you keep it away from heat.

 

[pcf_mark]

That length of vacuum hose may have durability issues over time. They are not made like they used to be and you are going to need to secure it along the way several times to keep it from coming off or being burnt. You can just get a length of brake line at the auto parts store and cut the ends off. Then you can bend a nice line that is not impacted by heat, oil, gas etc and you can secure it one place and it wlll stay there. A short length on each end to the source and modulator.

If you go to a pick-n-pull you may find a 70's Ford pickup or van and you can grab it from that. It will bolt right up.

 

[Tcb3078]

Thanks. I have it secure, just having D issues and it not shifting. Trying to eliminate the issues

 

[DJs74]

Double check to make sure the hose you're using has sufficient wall thickness. If you use to thin of a wall hose, it could suck closed under vacuum... basically collapse on its ID and then you get min to zero vacuum pull on the modulator.

On another note, if you used an adjustable modulator valve, you can adjust it's performance at the small set screw located in the vacuum port. A very short, thin blade, straight screwdriver is needed - little bit tight in that area sometimes.

Last, double check to make sure the pin was installed first into the port where you placed the modulator.


DJs74

 

[pcf_mark]

If you can describe it in detail ViperWolf can diagnosis it!

 

[Tcb3078]

No problem as long as you keep it away from heat.

Since they recommended it....

Haha. Ok, he is my trans issue.

Reverse works fine.
Drive starts, stays in first unless I manually shift to second and the back into D.
1st works fine
2nd works fine
D has no upshift and have yet to get into 3rd.

Vacuum checks out at 15.5 on manifold and same at the end of the hose.

As mentioned, I used fuel line from manifold all the way to the trans.

 

[Viperwolf1]

Since they recommended it....



Haha. Ok, he is my trans issue.



Reverse works fine.

Drive starts, stays in first unless I manually shift to second and the back into D.

1st works fine

2nd works fine

D has no upshift and have yet to get into 3rd.



Vacuum checks out at 15.5 on manifold and same at the end of the hose.



As mentioned, I used fuel line from manifold all the way to the trans.

What's the history on the C4? Was it working previously, just rebuilt, or new to you?

It might be missing the modulator pin or the valve behind it could be installed backwards.

 

[Tcb3078]

What's the history on the C4? Was it working previously, just rebuilt, or new to you?

It might be missing the modulator pin or the valve behind it could be installed backwards.

Rebuilt c4 5 years ago. Sat until I could start. Has a mild shift kit.

 

[Viperwolf1]

Rebuilt c4 5 years ago. Sat until I could start. Has a mild shift kit.

Check the modulator pin and valve. This is the correct orientation of the valve. Mod pushes against pin.

 

[Tcb3078]

Check the modulator pin and valve. This is the correct orientation of the valve. Mod pushes against pin.

Thanks Viper. Sounds like I was headed in the right direction. This was my next investigation point.

 

[Tcb3078]

Thanks Viper. Sounds like I was headed in the right direction. This was my next investigation point.

Just an update. Didnt do anything but drive it yesterday. D worked great, all three gears. Drove that way for about 10 miles. Stopped, the I couldn't fin 3 again and d wouldnt shift. I'm thinking more of a stuck governor? Still have fluid com ok ng out vent. Could overfilled be the problem?

 

[B RON CO]

Hi, check the kick down lever is not sticking down.
You should have a spring up at the top to pull the lever up. The kick down should move down and return by itself when you check it from under the hood.
Good luck

 

[Tcb3078]

What's the history on the C4? Was it working previously, just rebuilt, or new to you?

It might be missing the modulator pin or the valve behind it could be installed backwards.

Figured I'd give an update. Ended up pulling the trans. Builder said governor was very stuck and the valve bodies as well. Saw some wear on itches, so he replaced as well. Ended up throwing in a Hughes 2500 stall converter too. Thanks viper for your guidance.

 

[jckkys]

This would be a good time to reinstall the steel vacuum tube. The original design was there for a reason. Why do something different unless there is good reason? Ford never saw any reason to change the design over many years of C4-C6 production and millions of units.