TH400 Kickdown Always Engaged
10-24-2009, 02:24 PM
#1
TH400 Kickdown Always Engaged
I have a 74 with a TH400. As far as I know, the kickdown switch has always been connected. Just put a new engine/headlight wiring harness in and now my kickdown solenoid is always engaged. I replaced the switch and that did not help. When I disconnect the switch, the tranny shifts properly - but does not kickdown. When I connect the switch, the tranny seems to always be in kickdown mode as it won't shift out of 1st gear until approx 4600rpms. I have searched this forum and cannot find anyone who has had this same problem. Any ideas why I am always in kickdown mode with the switch connected?
Last edited by rcsdvette; 10-24-2009 at 02:46 PM. Reason: added more info
10-24-2009, 03:04 PM
#2
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Changing out that switch was a pita wasnt it? Its possible that your solenoid in the tranny (thats what your switch connects to is the problem). I say this because when you are hooked up its possible that you are keeping the solenoid active and it maybe sticking. Just a thought. BOL
10-24-2009, 03:04 PM
#3
Melting Slicks
Then you have a stuck switch. or it is not being activated by the gas pedal? Take the switch out, connect an ohm meter to it and see if the contacts change state when you activate the switch.
10-24-2009, 03:10 PM
#4
kickdown switch
I tested the switch before I put it in and again with it connected and the gas pedal engaged. Both times it worked properly. I am really at a loss...
10-24-2009, 06:56 PM
#5
Le Mans Master
unplug the wire from the tranny and using a volt meter check it, with the switch disengaged there should be 0 volts. have someone press the pedal there should be 12.
if you are getting 12v at the tranny with the pedal not to the floor the only explanation is that the switch is bad.
if you are getting 12v at the tranny with the pedal not to the floor the only explanation is that the switch is bad.
10-24-2009, 08:18 PM
#6
Team Owner
Could be the kickdown switch; could be the wiring; could be the adjustment on the switch (so that it is always closed). If you disconnect the 12v supply to that system, you should be able to perform continuity tests of the components and wiring in the system to see where the problem resides.
10-25-2009, 07:59 PM
#7
kickdown switch
All,
Thanks for the replies but I must have forgot to mention that the switch is brand new - and even though it's new I still tested it before I installed it. I will test the wire at the tranny next week and post results. In the mean time, if any has any more ideas...
Thanks for the replies but I must have forgot to mention that the switch is brand new - and even though it's new I still tested it before I installed it. I will test the wire at the tranny next week and post results. In the mean time, if any has any more ideas...
10-25-2009, 10:23 PM
#8
Team Owner
"New" parts doesn't really mean "good" parts anymore. Third-world manufacturers do things fast...not necessarily well. Time spent on inspecting product quality is wasted time, in their eyes. Anytime I buy a 'new' switch (or similar part), I check it for proper function. You would be amazed at the poor quality of new products these days. Use an ohmmeter to check the switch out, check to see that wires aren't shorted to ground...or to each other. You get the idea....
10-25-2009, 11:20 PM
#9
"New" parts doesn't really mean "good" parts anymore. Third-world manufacturers do things fast...not necessarily well. Time spent on inspecting product quality is wasted time, in their eyes. Anytime I buy a 'new' switch (or similar part), I check it for proper function. You would be amazed at the poor quality of new products these days. Use an ohmmeter to check the switch out, check to see that wires aren't shorted to ground...or to each other. You get the idea....
