TH 400 question
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Instructor
Joined: Feb 2003
Posts: 176
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From: jacksonville florida
TH 400 question
Can anyone tell me what the switch on the drivers side of the transmission is for?it looks like a small round device that has 1 wire going off of it to (I don't know where),My transmission does not downshift when I floor the pedal but it does shift when I depress pedal 1/2 way but that does not seem like a passing gear. could that switch be the problem? :confused:
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Joined: Jan 2002
Posts: 87
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From: BOULDER CREEK ca
Re: TH 400 question (hauk)
i think it goes to a switch that is under the dash and is made by the throttle rod off of the gas pedal. On my '69 there is a switch there with an arm that is only made at WOT. Always assumed that it was to force a down shift on the tranny, i think that your part throttle downshift might be from the vaccum modulator.
hope that helps.
hope that helps.
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: TH 400 question (HWY 9 - '69)
That's correct... The wire is to the detent solenoid. Part throttle downshifts are modulator controlled but it will never go back to 1st once it shifts up. and will not downshift from 3rd to snd and higher speed. The solenoid switch does all of those downshifs at WOT. So.... with the switch working correctly , if you are driving along at say 25mph in 3rd and you punch it, it will go back to 1st and upshift at or near the red-line. If you are going 60mph it will downshift into 2nd.
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
Re: TH 400 question (silvervetteman)
Could be the switch at the accel pedal - or the relay inside the tranny.
The previous owner of my 75 had the switch replaced - then needed the
relay replaced, also. The switch is relatively easy to replace. The relay requires
you to drop the tranny pan. Good time for filter change.
:seeya
The previous owner of my 75 had the switch replaced - then needed the
relay replaced, also. The switch is relatively easy to replace. The relay requires
you to drop the tranny pan. Good time for filter change.
:seeya
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: TH 400 question (silvervetteman)
The wire is for the kickdown detent. What you see on the outside if the trans is not actually the solonoid. Its just a connector that allows the wire to pass thru the case and get to the solonoid which is attached to next to the valve body inside the pan. The solonoid is activated by the switch above the gas pedal. As stated above, if everything in the kickdown sys is in working order, the trans will kick down from 3rd to first from a 30mph cruise. If its not working it will only kickdown to 2nd as activated by the modulator. When working correctly it will cause a kickdown from 3rd to 2nd from a 60mph roll. if not working, it may just hang in third when floored from highway speeds.
