Discussion in 'The "Juice Box"' started by 67 Electra Cvt, Apr 5, 2021.
I didn’t even realize it and hope I haven’t steered anyone down the wrong path.
In 1967, your Electra would have gotten the BT coded ST400. For all intents and purposes, it is the same as a THM400 EXCEPT that it is a switch pitch. The 2nd connection at the transmission is for the switch pitch feature (which does not work the way your car is now)
You should verify that your car still has the original transmission. The tag on the passenger side of the case should look like this,
An explanation of the switch pitch transmissions,
If you have a legitimate 67 400, the upper lug is for switch pitch,
and the lower lug is kick down. You definitely do not want them
shorted together. If you do not have the second wire to the upper
lug, you are completely missing out on the features of a switch
pitch. However, do try it with no wires connected. Bruce Roe
I will check the tag on the side of the transmission, but after seeing the 'shoe heel' indent on the pan and the 2 blades for the electrical connection, I'm certain it is a ST400.
I have not driven it yet without the disconnecting the wire to the trans. Hopefully, I can do that this week.
If it is the governor causing the problem, can a new TH400 governor be used? And the same for the modulator?
I am still looking for the SwitchPitch carb relay if anyone has one for sale.
Thanks everyone for all your input and help.
For the heck of it. go to ebay.. buick lockdown switch... Hit the Used filter...... usually about 10 pop up... then by looking at the pic's figure out which one you have...... Hopefully the one on your car car is the one... from the pic it looks short... there are longs also... ETC ETC.
There's this one............
There is a switch pitch fix that eliminates the problematic switch on the throttle linkage at the end of the arm to a dashpot that takes the place of the stock dashpott in it's place. Eliminates also the problematic adjustmants.
Thanks for the replies. I might the dash mounted switch once I get the current issue sorted.
Can a governor and a modulator from a TH400 be used in the ST400? If I'm going to check both, I'm thinking of replacing each while in the process.
Yes. Instead of wasting your money, test your current components. There is a difference between auto mechanics and parts changing. The modulator is good if it holds vacuum and there is no ATF on the vacuum side. The governor is good if the weights and valve in the stem move freely.
Spot on. And I've never had it happen to me, but if the modulator valves inside the valve body are stuck or only partially moving somehow, that could affect shift points even with a good modulator.
See parts labeled 320-332.
Just unplug the wire... Do you really need the passing gear kick-down? If the switch was inoperable the other way... ( no power getting though it ). Would you even know it was broke???????
Personally highly dought it... Mine is missing the clip that holds the rod on the carb..... Im just to lazy to fab up another way to hold the rod on the carb... Also I did buy the modern vac switch but I dont know where I put it..
Shawn, I just saw this thread and I mostly agree with these guys. If the switch is not hooked up, and it shifted before, then it's probably something else like Larry, Bob and Devon sad. The modulator, valve behind it, the governor or vacuum. I'm not a trans guy (but I know of one in MA). I suppose it could be linkage, or cable stuff if it has a floor shift. Only you know what you messed with on it, since the problem popped up. I disagree with Tom, the dash pots are fine. Why re-invent the wheel? Two things: w/o looking at a wiring diagram, I remember that power wire is on a fuse for something else. Wipers? I forget, but if the fuse is blown... Second for Bob, that "top hat" clip is readily available.
Forget the fuse.... It the fuse is shot that would not the pitch switch (click noise) or the passing gear to engage (click noise)
In the pic you posted the rod is missing.. the rod makes power go through the switch....Or removers power from switch......
Could be over time with no rod attached to the down shift/varible switch it has fllen down to the point where the system believes it's ALWAYS full, WOT, all the time .
Another problem is the governer could be stuck at which time could cause the same problem. Easy to check & IF nec. take apart & clean.
Agreed with above. Disconnecting the plug on the side of the trans takes the guessing out of the original electrical switching arrangement, well worth a try.
To add to the "weird things" that can happen though, I've read of the detent (kickdown) solenoid getting stuck too! If that happens, taking 12V away won't help. Again, I've never seen it happen, but throwing it out there for more info.
Thanks again for all of your input. I disconnected the plug on the trans and it now shifts. I still need the linkage at the carb. I'd like to restore it back to the factory spec. than add the switch on the dash.
Now the bigger problem is miss firing. Never used to. Has a Petronix distributor on it. Checked all the wires and plugs. Fuel is brand new. I have to check the timing. I know this is a trans forum, but just wanted to update.
Depending on the Pertronix generation you may have asked and answered the same question. The early ones were terrible, mine only took a couple months before the misfiring and I instantly went back to points, never to return. "You'll never have to fuss with points again!" was a bad meme then and still is.
X2......... I bought a 67 special as a drivable parts car (floor rotted out)came with a pertronix. Got about 10 mpg. replaced with points 15ish mpg....
With the distributor up front on the Buicks. Why bother with electronic kits...
God Bless you sir.
This too. Even in the back, you just lean over from the fender, instead of the radiator and grille. Looking back now, easy to see the power of advertisement to invent a problem for every solution.
I put in the Petronix electronic kit to replace the points only because I thought it was reliable. It has only been in the car for a year. I have to check to see if it is in fact the issue.
Regarding the ST400, I was going to drop the pan and replace the filter because the pan is leaking. I was told I have to 'redimple' the bolt holes because the aluminum can become pulled when it was originally tightened. Has anyone heard of this?