What causes the downshift?

[ClarkDart70]

Is it the action of the lockdown linkage "bottoming out" as its pushed all the way back

Or


The action of it moving rearward quickly?


I cannot seem to get my car to downshift under heavy acceleration. 360 with a 904.

 

[RustyRatRod]

It's not that simple. There are several things involved. First you should start by adjusting the kickdown linkage. With the throttle all the way open, you should adjust the linkage so that the kickdown lever on the carburetor is all the way back. Do this as a base adjustment. Drive the car and report back. Also, do you have a factory service manual for your car? If not, get one.

 

[ClarkDart70]

Did it. No down shift.

 

[Oldmanmopar]

Kick down is only for throttle pressure and passing gear. If you put a part throttle kick down servo on the valve body from a /6 for a 904 or a truck for a 727. It will downshift under the slightest touch of the pedal. three screws is all it takes no adjusting.

Flat out shifting is controlled by the governor and throttle pressure linkage. Most performance cars did not come with part throttle do to traction loss when downshifting. If you had a sure grip you didn't get the part throttle.It was a Safety issue.

 

[funwithfuel]

that's a cool piece of information I did not know

 

[TrailBeast]

Slightly low mainline pressure in the trans will cause a loss of kickdown shifting also.
Next time you service the trans turn the pressure regulator valve adjustment on the valvebody about 2 turns counter clockwise and see if that fixes it.
This will raise the main hydraulic pressure in the whole trans and force the governor to react to the WOT a little sooner.

It's the allen screw at the end of the metal bracket by the manual valve.

 

[Oldmanmopar]

The arrow points to the plate you remove to install the servo. Three screws

I use to work at a trans shop when I was younger ,as a installer. They were noted for making Mopars shift better. installing the servo is all they would do . besides cutting the center out of the governor piston on a lathe.

Cutting the governer would raise the shift point to a higher RPM under flat out operation only. Only 340's and max wedge cars came with the lighter governors. They would hold the shift from 5500 - 6000 in drive from the factory.

One other thing is when you have a auto valve body always take off in drive and the pull it to low after the car is moving. Low in the selector is a different gear then 1st gear in drive.

It will shift second much better using this method and also be more responsive taking off.