hey guys I have a 84 f250 351w c6. I don't know what's done to the c6 but shifts very good. I'm thinking it has a shift kit. Because it shifts hard into second and is very firm. I have an adjustable vaccine modulator on it. And I have it turned in a couple turns. Just wondering I have no kick down. .... Going up a hill it still kicks down to second. How?

 

It uses the vacuum modulator for that.
Dave - - - -

 

+ the governor in the trans. Modulator tells it the load, governor tells it the road speed.

 

My pickup (C6) runs in 2nd gear from 10mph to about 45 max under full throttle. Don't forget these pickups weren't designed to go much over 55 mph because the law at the time didn't allow it. That's why the gearing is so low. I can hardly ever get my pickup to kick down to 1st gear. It likes to ride in 2nd most of the time since I normally only drive it around town. Over 30mph will shift to 3rd if I don't have it floored.

If you wanted to know how it works, the vacuum modulator hooks up to the engine vacuum system. There's a certain amount of vacuum required to suck back the diaphragm/pin (usually minimum of 14 psi of vacuum). When the engine vacuum pressure drops due to acceleration (air from carb being open filling the vacuum void), the pin is pushed forward which pushes the throttle valve open.




The way the governor works is pretty slick too. It has a couple "valves" springs pushing them closed too. This one, though, is attached to the output shaft which spins when the vehicle is moving. As it spins, the centrifugal force pushes the valves outwards compressing the spring and opening the valve so that fluid can flow through.



Hope this helps someone understand how the C6 transmission functions better.