1970s 1974 Cadillac Eldorado Transmission Shifting Problem

[motard]

My 1974 Cadillac Eldorado all a sudden will not shift out of 1st gear. It is full of fluid. What could be some of the causes?

[TJ Hopland]

There is a 2 wire switch on the drivers side of the carburetor linkage, this is the 'kickdown' circuit.  If this is stuck on it won't wanna shift.  If you just unplug it that will disable the function.  If it then shifts normally during normal driving you found the problem.  It activates when you put it to the floor so for many classics you won't even know its not working if its just a bad switch. 

This vintage Eldo is also very hard on one of the transmission linkage pivot bushings so make sure you are carefully counting the clicks and are for sure in D.   If you are just going by the pointer you could just be in the wrong gear.  If this is the issue its important to get it fixed because it may not reliably go into and stay in park and you could have the car get away from you.       

[Big Fins]

Looking down the side, next to the transmission dipstick, you will see a cap held on by a spring clip. Inside of this is the governor. A sheared off gear or broken spring may also be the cause.

I've heard from many people that this cap is held on by the spring clip because the governor so often goes bad. I have no experience in this short of just removing the speedometer cable to lube it. Just a little info before some shop tries to sell you a transmission.

[J. Skelly]

possibly the transmission's vaccuum modulator

[motard]

Guys thanks for your assistance. TJ Hopland I checked out the kickdown switch per your instructions and it was the problem. I disconnected the wires to it and the car shifted just fine. I will buy another switch. Thanks for saving me again. (You also had the correct answer when my blower motor would not shut off a few months ago.)

[Big Fins]

Wondering if you tripped the switch by pressing the pedal to the floor to set the choke for a cold start.

[TJ Hopland]

I didn't ask and you didn't say how hard you tried to get it to shift but its been my experience that if its the vacuum most people can and will push it hard enough that it shifts.  When the electric is stuck on I'm not sure that it can, if it can its a few R's over where you would think the engine would explode so most people won't try and push it that far.

I think those switches can be hard to find but unless you do a lot of highway driving and passing you may never know its not there so you can still likely enjoy the car while you are waiting for a reasonable deal on a replacement.  Make sure you tie and or tape the wire up out of the way so it doesn't get in the linkage or melt into the intake.  That's a + voltage signal and its tied to something else, AC clutch? So if it shorts and blows the fuse you loose other things.  

Probably 90% of the time I have driven 90% of the 400/425 equipped cars that system hasn't been working for one reason or another.  I would imagine they were reasonably reliable when new but all forms of the switches I have ever seen have some to a lot of plastic in them that just didn't hold up over the years.   

[Big Fins]

It's usually the Bakelite arm that breaks off from stabbing the throttle too hard.

[35-709]

I have drilled out the little brass rivets and taken those switches apart, cleaned up the contacts and returned them to service.  Be very careful of the little arm on that switch, if that gets broken (easy to do), then you are for sure looking for another switch.
Been too long to remember what I held it together with once reassembled, maybe 3/32 pop rivets.  The hole in the bottom of the switch is to adjust it once reinstalled (with a #42 wire gauge drill bit), the procedure is in the shop manual --- Page 7-44 in my '73 manual.

[TJ Hopland]

Are they sprung so if the arm breaks they are stuck on WOT?

[Big Fins]

They are sprung, but it returns to the closed throttle position if that arm breaks.

[Jeff Rosansky CLC #28373]

For what it's worth, the kick down switch on my 70 Deville has been broken for about 7 years now...... And she has no trouble shifting, or passing other cars.
Not that I do that of course (Just in case someone from Hagarty is on the forums😉).

[TJ Hopland]

I was thinking broken arm would would be the not triggered position.   The one I took apart or had fallen apart, don't remember the year or model a little nub broke off that the spring acts against so the spring just unwound.