C4 trans vacuum

Hi, I did some searching but did not come up with the help I need. I have a C4 ford trans and it shifts hard and late, I am running a tunnel ram with 2 edelbrock 1404's and it is currently hooked up to ported vacuum. This is how it was set up when I got it but by doing some searching on HAMB I see this could possibly be wrong, if so where do I need to hook it to? There is no port in the manifold so is there any other options? Should I install a vacuum pump? Any help would be great. Thanks

 

I was told by a good transmission guy that the hard and late shifts can happen if you do not have a kickdown linkage from your throttle hooked up to the C4.

The kickdown does a couple of things, besides the obvious kicking down of the trans to a lower gear when needed, it also regulates the transmissions pressure when at WOT so that the pressure is where it needs to be for proper shifting.

Without it the trans does not get the high pressure when and where it needs it and will shift late etc.

Of course another issue could be where your vacuum modulator is hooked up to and even how it is adjusted.
Maybe someone will add in the proper place to get vacuum to the modulator.

 

trans gets manifold vacuum.

 

Yup, manifold vacumn. I've run without kick downs with no problem. How much vacumn are you getting if your cammed out with a tunnel ram. I think you can adjust the vacumn with a little allen head screw inside the canister by popping off the little hose.

 

Manifold vacuum. If it won't shift then and you can't adjust the modulator, you could try changing the modulator or install a manual shift kit. Have you tried manual shifting?

 

Not sure about your carb but you say you were running ported so your saying also you have no other options. You don't have a port at the base of the carb?

 

I've had a C-4 with no kick-down for 16 yrs and no problem. I'd check vac. mod/ adj and use manifold vac.

 

If I remember correctly, on a C-4 the kick-down linkage only does that and nothing else.

Per what others have said, the modulator should be connected to manifold vacuum, not ported vacuum.

Should you need it, adjustable modulators are available.

If you have a supercharger or really radical cam, and you don't want to go with a FULL manual valve body(not too friendly for the street), a mechanical throttle pressure conversion can be used to eliminate the existing vacuum components. I haven't seen a mechanical set-up for a C-4, but most likely someone make it.

 

Ditto, manifold vacuum, and adjustable modulator.


4TTRUK

 

Several modulators are available, and one tranny guy told me the little rods come in different lengths as well. Try hooking the vacuum signal to the bottom PCV port on one of those carbs. That may change everything.

 

Get a dual port vacuum modulator! Those things work great!