C-4 trans not right under boost.

[Anonymous]

Everything is doing great on my turbo six but I am having a hard time getting the transmission to do right under boost. I had a one way valve on my trany vacume line and it slipped bad from 2-3 under boost so I pulled the valve out(after making 100% sure it was working and on the right way) and hooked it straight up into the intake. Now it will not shift out of second untill I let off the gas and get to 0psi. What gives? Is there something I am missing?

Dan

 

[xctasy]

It never is unless its a draw through.

The modulator must 'see' the same vacuum scenario as it did on the carb BT (Before Turbo). I'd use a vacum canister, and mount the vacuum line upstream of the turbo. There are some pieces that help, but most guys are running turbos with fully maniualised C4's, so you'll have to work through the vaccum needed. This was covered a while back in early 2003 on the Hardcore or Drivetrain forum.

Can't find the link yet.

I just used a Ford Prefect vacum can, and rigged up a separate line for my Impco CA 300 blow through. There's possibly another way of doing it. What did early Mustang 2.3 Turbo's do? Or the auto T-bird turbo coupes?

 

[Does10s]

Manual valve body!

 

[Anonymous]

Manual valve body!

IF YOU CAN FIND ONE THAT WILL FIT MY 66 C-4 I WILL BUY ONE!

DAN

 

[Bort62]

Run the Vac line for the tranny into your intake ducting before the Turbo.

 

[Lazy JW]

I once owned a 1955 Ford (272 Y-block V-8) that had vacuum powered windshield wipers. The fuel pump was a two-sectioned gizmo that was part fuel pump and part vacuum pump so as to keep the wipers working while going up hills, etc. Would there be any chance of adapting one of those fuel pumps onto your engine? A lot of fuel pumps interchange.
Joe

 

[Falcon62]

All early Falcons were equipped with vacuum powered wipers as standard equipment, so the dual diaphragm fuel pumps are out there (I have a few), and would be a bolt on. However, I don't know if they would provide adequate fuel volume for a non-NA induction system (easily resolved with an electric fuel pump).

 

[Anonymous]

IK;
perhaps a little theory will help here:
The C4 holds to the lowest gear it can when there is no vacuum on the modulator. The gear is then determined solely by the governor and internal pressures.

That said, if you can find a place (like Bort62 suggests) where the original MANIFOLD vacuum is mimic-ed, the problem will go away. The vacuum must be high (like 8 inches or more) to upshift. Below about 6 inches, it will downshift, like you're standing on the throttle.

If you have an adjustable modulator (try a small screwdriver or Allen Wrench into the hole to find out), try turning it CW (I think that's right) to desensitize the downshift. When these units get a hole in their diaphragm, 2 things happen: 1) it starts burning tranny oil through the engine and 2) they shift into high gear before 30 MPH no matter how hard you accelerate because the vacuum is not pulling on the diaphragm to delay the shift (non-SelectShift models) or they get stuck in low gear (SelectShift models).

 

[Crosley]

Seems like a 67-69 valve body can be used on your 66 tranny.


TransGo offers kits to convert the 67-69 vb to full manual operation.

Manual valve body!

IF YOU CAN FIND ONE THAT WILL FIT MY 66 C-4 I WILL BUY ONE!

DAN

 

[MustangSix]

I'd first check two things, as suggested above. First, make sure there is a check valve which prevents positive pressure from reaching the modulator. Second try adjusting the modulator.

You may have to mimic vacuum. You might be able to do that by adding a vacuum canister between the modulator and the checkvalve. Or you could go to something very sophisticated, like the vacuum control vavles used on Mercedes Benz diesels. Diesels have no manifold vacuum, but Mbz used a throttle controlled bleed valve to operated the vacuum modulator on its transmissions.

Perhaps the best thing to do would be to call Art Carr or Baumann Engineering and ask the best way to hook it up.