Q. What is the most complex component on modern cars?
A. The automatic transmission
Q. Should a novice attempt to work on a TH400
A. Sure why not, what could go wrong?

Ok here's the deal, my 68 TH400 wouldn't kickdown, otherwise working great. Messed around with the switch on the gas pedal, no luck.
Hooked up a remote switch to the leads on the gas pedal switch and lifted the car.
When I throw the switch I get 12 volts to the kickdown terminal on the tranny, but no "click".
So I ordered a new Kickdown solenoid online and tonight pulled the tranny pan. Pulled out the old solenoid. It looks different. More on that below. I tested it out of the tranny and it now "clicks" and actuates. Maybe an intermittent problem.

Question 1.
If the kickdown solenoid is working, what else could be the problem?

Question 2.
Look at these two kickdown solenoids. The new one is on the right. It looks less robust. The old one has a round disc with a tiny hole that a tapered needle/pin centers in. There is also a shim that you can see next to it. The new one has a litte circular "screen" instead of the pin/disk.
I think I'll go ahead and put in the new solenoid.
Should I put the shim in with the new solenoid or leave it out?
Is the new solenoid correct despite it's different design?
(ok that was 2 questions)


Question 3.
The pick up filter has a tube with two O rings. I just kinda pulled it down to remove it. One O ring is still in the bore, the other is on the tube. Should I just shove it back in?



Question 4.
While looking over the tranny, I found this connection "nipple" on the right side, top of the case with nothing attached to it. What is this? What should be attached?




Any help appreciated!
Fred

 

I believe the shim is actually a gasket. If filter is not new get a new one and pan gasket by ATP. Two o-rings on pickup tube is recommended by some. ATP also has the o-rings. Place both rings on end of tube spaced about 1/8 in. apart, lube with some fluid and push into case. I did this on mine and ok so far. Other members will know more. mike...

 

The tube your seeing at the top of the trans is a vent. It's correct as is.

 

I have seen on many occasions the kick down stops working after a shift improver kit is installed. Does your trans have a shift kit in it?

 

I would not be surprised if it does. I didn't install one, but I know the tranny was "rebuilt" a few years by previous owner, and I notice it shifts quit hard from 1-2 with even moderate acceleration.

What would be the fix?