c4 hard shift

[bigblue72]

hi ive have a 72 sportcustom 302 and c4 trans the problem i have is when i put it in gear it engages hard doesnt matter if its foward or reverse and then while driving it will upshift thru gears but not until it reaches about 4500-5500 rpm or so and when downshifting it downshifts late and hard someone pleasehelp ilke this truck its my 4rth one and id like to keep it on the road

[1972hiboy]

Did this problem come on all of a sudden? Something you may want to check is the shift modulator. its vacuum operated. I would check to make sure you have FULL manifold vacuum plumbed to it. also check to make sure the vac diaphram inside isnt blown out.

[fordman]

read this thread. http://www.fordification.com/forum/view ... =4&t=57456

[bigblue72]

where would i find the modulator and governer so i can inspect both and no it didnt all of a sudden happen it was like that when i bought the truck its the exact same issues the gentlemen with the c6 had

[fordman]

it is 7a377 in this diagram. it is a extrenal parts of the transmission. up under the back with a rubber hose sticking out of it. inside where the rubber hose hooks up is a screw that can be turned. http://www.fordification.com/tech/images/c6_05.jpg

[1972hiboy]

The modulator is underneath by the transmission pan on the passenger side...it should have a rubber hose coming off of it. it should be round. Fordman is correct when you disconnect that rubber hose there is a allen scren down inside the metal tube that can be adjusted in or out. id make sure first that you have the vacuum lines hooked up to manifold vac and that it is indeed ran down to the modulator. If you have a vacuum pump id hook it up to the modulator and make sure it holds for a few seconds....

[70_F100]

Good advice, so far.

Stuck governor would act like what you've got, if the pistons were stuck in the "low speed" position. The governor is telling the valve body that the output shaft is turning at low speed, thereby holding it from shifting. There is a point at which line pressure overrides the governor in most automatic transmissions. Ever locked a GM TH400 in 1st gear and drove it as hard as you could? The transmission will shift to second with a "BANG" once the engine RPM's and vehicle speed reach a certain point.

Other things to check:

Since it engages hard when shifting into reverse or drive, what is your idle speed?

Since your shifts are so high, there is a possibility that the kickdown linkage is binding, or that the kickdown valve in the valve body is stuck.

You say it's a C4, and it had these symptoms when you got the truck. Is there a chance that someone has changed the filter? There is a small valve, spring loaded, that will fall out when the filter is removed. If you don't have any success with the other suggestions, you might want to pull the pan and filter and make sure that the valve and spring are installed correctly. The valve is like a little ,minature toilet plunger. It has a large end that is cupped, and the other end would be sort of like the "handle" on a plunger. Make sure that the large, cupped end is inserted first into the valve body, with the handle pointing toward the filter, and the spring over this handle. Then, the filter is installed and it holds all of that in place.

Good Luck!!!!