Fluid drive won't down shift.

[R.B.Newport]

Fluid drive on my 50k mile '50 Chrysler won't downshift when slowing to stop then when I depress clutch pedal while stopped it downshifts. There are many components involved here: the direct drive piston (or shuttle valve) inside the trans, the interrupter switch or the anti stall unit on carb. It upshifts just fine. The previous owner had some 90 weight in it which I replaced w/ dextron simply to free up shuttle valve but no luck yet. I know a certain hydraulic oil or 10wt. engine is what's recommended.    Oh, one other thing , if I were to gently take off from stop sign w/o having depressed the clutch to effect the downshift it pops out of gear! leading me to think shuttle valve was not engaged all of the way to begin with do to sticking.  I'd appreciate any insights, Thank you.

[Rusty_OToole]

I would start by changing the oil to TDH tractor oil, ISO32 or ISO22 grade. Normally the trans will shift down even if the wiring is not connected. There is a valve that controls the shift, it may be sticking.

[61polara]

You should also check your idle speed.  It should be 400-450 rpm.  A high idle speed will prevent the downshift.  By depressing the cluch when you come to a stop, you are faking a lower idle speed.