TH400 Detent(kickdown) solenoid question
04-28-2021, 09:08 AM
#1
Melting Slicks
Thread Starter
TH400 Detent(kickdown) solenoid question
What would be the symptoms of a leaking solenoid be?---the rubber seal that seals the solenoid to the valve body.
I can hear the solenoid clicking when I actuate the kickdown switch with the accelerator pedal (key on/engine off), so I'm assuming the switch/wiring/solenoid are fine. But after it's in 3rd gear, say around 3000RPM, there is no kickdown. BUT----it will kick down to 2nd under 2000--2500RPM.....
Thanks for any advice!
I can hear the solenoid clicking when I actuate the kickdown switch with the accelerator pedal (key on/engine off), so I'm assuming the switch/wiring/solenoid are fine. But after it's in 3rd gear, say around 3000RPM, there is no kickdown. BUT----it will kick down to 2nd under 2000--2500RPM.....
Thanks for any advice!
Last edited by shoptek; 04-28-2021 at 09:21 AM.
04-28-2021, 09:32 AM
#2
Race Director
the soleniod lets a check ball open to downshift. if the ball leaks, it stays in kickdown. i bought a 66 catalina convert with bad trans for 300 bucks. dropped pan and straightened out the spring lever that wasn't holding the check ball in the hole. sold it for 1k. thought i made a killing...
04-28-2021, 10:15 PM
#3
Team Owner
Those little solenoid switch/valve gizmos mounted to the bottom of the transmission valve body are prone to failure...either electrically with a fried coil or broken wire to the coil, or mechanically with a plugged-up orifice which doesn't allow the pressure to bleed off. They are relatively easy to change....once the sump pan and oil are drained/removed 
.; but replacements for them are complete junk. If the solenoid is 'clicking', the coil is still OK--it's likely just plugged up. You could remove it, clean it out, and reinstall it. But check it out functionally by putting 12vdc to the connector wire and ground to the casing to actuate it. Then make sure the passage is open.
There is some chance that the problem is downstream of that valve. But that is much less likely.
.; but replacements for them are complete junk. If the solenoid is 'clicking', the coil is still OK--it's likely just plugged up. You could remove it, clean it out, and reinstall it. But check it out functionally by putting 12vdc to the connector wire and ground to the casing to actuate it. Then make sure the passage is open.There is some chance that the problem is downstream of that valve. But that is much less likely.
Last edited by 7T1vette; 04-28-2021 at 10:16 PM.
04-28-2021, 10:34 PM
#4
Nam Labrat
Member Since: Sep 2013
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After removing the solenoid and testing it ...... would it be safe to apply about 50psi of shop air into the bore that the solenoid fits into in order to clear the passageways out?
I would have to study a diagram of the valve body to see which valve would "catch" any trash that the air pressure forced "downstream".......
and remove that valve before applying air pressure.
I would have to study a diagram of the valve body to see which valve would "catch" any trash that the air pressure forced "downstream".......
and remove that valve before applying air pressure.
04-30-2021, 07:02 PM
#5
Team Owner
The solenoid valve captures the trash. When blocked (or with limited flow) no downshift will occur when solenoid is activated.
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