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Switch pitch question

Started by Gary McKinney, May 26, 2019, 12:30:17 PM

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Gary McKinney

I recently had the transmission in my 1966 Eldorado serviced with new filter and fluid change (routine maintenance, it was working perfectly).  I’ve noticed that after sitting at a stoplight with the brake on, when I take my foot off the brake pedal there’s a second or so delay while the stator changes pitch.  Is this normal?  I don’t remember it doing that before, but I haven’t driven the car in several months and perhaps I just don’t remember how it behaves. Otherwise, the transmission shifts fine.  I want to be sure everything is operating properly before driving it to Louisville in a couple weeks! 
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

Gary McKinney

The plot thickens.  I took the car out, got about 300 yards away and the transmission would not shift out of first gear.  Reverse is fine.  Checked fluid level, very low.  Topped it off, still no shift out of first.  Transmission does not leak, and there’s no fluid in the coolant, so the only place  I know that it could go is into the engine via a bad modulator.  When it rains it pours.  And it’s pouring now! 
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

35-709

Yes, a bad modulator would be my first suspicion.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

TJ Hopland

Would be worth checking that the vacuum line just didn't get knocked off.  No vacuum signal would make that part of the trans think you were wide open and delay shifts.

Or an electrical issue?   Both the pitch and kickdown are electric.   Maybe in a test drive the pedal got stomped a little harder than usual and the switch(s) are stuck on?    I would think a test for that would be to unplug the connector from the side of the transmission.   If you do that with the key on and you hear a click you know at least one of those solenoids was on.    The kickdown for sure gets power to kickdown so no connection you won't get the kickdown function.   I have no idea which way the pitch goes with no power.

I don't know what the filter setup looks like on this but you hear more and more about filters that don't quite fit right or don't get installed correctly on this old stuff than you used to.   Stuff like either just a crap part or things like the gasket staying stuck in the body so you end up with double gaskets that don't seal.   Or maybe there was supposed to be a gasket and there wasn't one in the box and the tech didn't know there was supposed to be.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

67_Eldo

I have a '67 Eldorado, but I recognize the situation.

The problem could be even simpler than the vacuum modulator. It could be a leak or a disconnected vacuum line *to* the modulator.

Many times when I get a little overzealous in re-routing wires/vacuum lines under the hood, I accidentally tug on the vacuum line that connects the carb to the vacuum modulator. Although my rubber vacuum connector is in OK shape, it doesn't require too much force to pull from the carb. If I haven't removed the air cleaner, I won't even notice that the vacuum line has been disconnected. So start there.

The next place to check is at the other end of the hard vacuum line to the transmission. The rubber connector can come loose/leak down there too.

This should have nothing to do with the switch pitch. The switch pitch (which I also have) is electronically controlled. The expert on all things switch-pitch-ian is Bruce Roe. :-)

bcroe

Quote from: Gary McKinney
I recently had the transmission in my 1966 Eldorado serviced with new filter and fluid change (routine maintenance, it was working perfectly).  I’ve noticed that after sitting at a stoplight with the brake on, when I take my foot off the brake pedal there’s a second or so delay while the stator changes pitch.  Is this normal?  I don’t remember it doing that before, but I haven’t driven the car in several months and perhaps I just don’t remember how it behaves. Otherwise, the transmission shifts fine.  I want to be sure everything is operating properly before driving it to Louisville in a couple weeks!   

Understand, the SWitch Pitch function is completely independent of
other trans functions such as shifting.  SWP is only controlled by 12V
applied to the upper trans terminal, for high stall.  Things like modulator
hose can throw off shifting, also kickdown in some situations. 

I believe there is a control switch by the carb, which should read 12V
on one terminal with ign on.  The other 2 wires go down to the trans,
the kickdown wire (bottom vertical trans terminal) should receive 12V
near max throttle.  The stator wire (top horizontal trans terminal) should
receive 12V at idle, none off idle, and 12V near max throttle.  So you are
in high stall at idle and WOT.  I believe some cars also had a small diode
off the brake light switch, also capable of sending 12V to the stator wire
when the brake is on.  Did we discuss this before? 

A small (to protect the diode) test light to the trans wires should verify
these functions with just ign on.  If all good, I would suggest that any
trans that age would require an internal seal refresh, regardless of low
miles.  I would keep the original hard parts if not worn.  This approach
does not go well with a trans shop, which will want to throw away many
good parts and replace them with possibly lessor quality.  Worse, they
have no respect for your SWP, likely will throw that away and put in
fixed pitch parts already on their shelf.  This is a loss, a really big one
if you use an electronic SWP controller to enhance the car.  Another
reason I do my own work. good luck, Bruce Roe

Gary McKinney

I hear the click in the transmission when I depress the switch next to the carburetor, which should indicate that the SP solenoid is working. However, according to the shop manual, the actual changing of stator pitch is accomplished with oil pressure. I’m assuming that bad pressure resulting from a bad modulator could also affect stator angle operation. 

And yes, there is also a switch on the brake pedal to change stator angle. 

I’ll have my mechanic check the vacuum line, and probably just try a new modulator (they’re cheap and apparently easy to replace).

Bruce, thx for the input.  As for having the transmission serviced, I’d be afraid to take it anywhere locally, although one of the shops here in town has been in business since 1950, one would think someone  there would be knowledgeable in these transmissions. .

If I don’t get this sorted out before the GN, I’ll be driving another Cadillac to Louisville.  😕
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

bcroe

Quote from: Gary McKinney
I hear the click in the transmission when I depress the switch next to the carburetor, which should indicate that the SP solenoid is working. However, according to the shop manual, the actual changing of stator pitch is accomplished with oil pressure. I’m assuming that bad pressure resulting from a bad modulator could also affect stator angle operation. 

And yes, there is also a switch on the brake pedal to change stator angle. 

I’ll have my mechanic check the vacuum line, and probably just try a new modulator (they’re cheap and apparently easy to replace).

Bruce, thx for the input.  As for having the transmission serviced, I’d be afraid to take it anywhere locally, although one of the shops here in town has been in business since 1950, one would think someone  there would be knowledgeable in these transmissions. .

If I don’t get this sorted out before the GN, I’ll be driving another Cadillac to Louisville.  😕   

Check the external stuff first, if that doesn't fix it, the trans will need
to come out.  I would start with good vacuum to the modulator. 

There are 2 electric solenoids in the trans, make sure they both
click in the proper sequence.  A click coming off idle, 2 clicks as
WOT is approached, same in reverse releasing throttle.  Pressing
the pedal will make sure slack in the linkage is not throwing it off. 
I can not tell you how many conversations I have had with Cad/
Buick/Olds owners about sorting out the unreliable switch.  Some
solenoid wires have the insulation fall off inside. 

Once the external stuff is right, the solenoids control hydraulics,
requiring the pump turning.  Never seen a problem there yet. 
The switch pitch solenoid controls a piston in your front cover,
which operates a big valve, which controls fluid to a really big
piston in the center of the torque converter, which changes the
angle of the stator blades.  There are ways to test the functions
if needed.  Bruce Roe

savemy67

Hello Gary,

As others have posted, check the simple things first, like the hose connections for the vacuum modulator, and the switch pitch switch at the carb and transmission case connections.  The shop manual has the proper diagnostic procedure.

If the modulator is bad, the transmission fluid sucked into the engine's intake manifold would most likely produce a large amount of white smoke.  While a new modulator is inexpensive ($15 to $25 for the part), my '67 shop manual suggests checking the governor first if the car does not shift out of first gear.  A governor repair kit is also inexpensive.  The governor and modulator can be removed without dropping the transmission.  If the nylon gear on the governor looks like a chewed up apple core, that is the most probable reason for no upshift.

The filter on a '66 is a canister type - a rectangular box with a tube and pick-up.  Early '67s use the same filter.  Later '67s used the flat, broiler pan style filter.  A shop that is not in the know may install the wrong filter.

I encourage you to read the shop manual a couple of times so you have a good understanding of the operation of your transmission, especially if you are going to have any work done by a shop.  Good luck.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Gary McKinney

I've checked the connection to the modulator and it seems tight and leak free.  I've never seen any smoke from the exhaust, but all that transmission fluid had to go somewhere and there's none on the garage floor.   That's a mystery in itself.  I can hear the clicks inside the transmission when I depress the switch by the carburetor, as well as when I depress the brake pedal.  That's about all I can do here at home, so the car is going to the transmission shop tomorrow for a full diagnosis and (hopefully) repair.  I'll report back with the findings.
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

Gary McKinney

It turns out that the downshift solenoid is the culprit.  With it disconnected the transmission shifts just fine.  The modulator checked out OK, and whatever pressure/vacuum readings were taken were correct.  For now the downshift solenoid will remain disconnected, but will be replaced after I get back from the Louisville GN. 

Thinking back over the 25 years I've had the car, I don't ever remember forcing a downshift.  I wonder if the solenoid has ever worked since I've owned the car.  Is it possible to hear the clicks but the solenoid still not function?  Whatever the case, as it is now the car drives just fine.

The last thing on the agenda before driving to Louisville is to replace the 13 year old Goodyear Regatta tires with only 6800 miles on them.  Hate to see them go, but I don't trust tires that old at highway speeds, even though they look brand new. 

Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

bcroe

Quote from: Gary McKinney
It turns out that the downshift solenoid is the culprit.  With it disconnected the transmission shifts just fine.  The modulator checked out OK, and whatever pressure/vacuum readings were taken were correct.  For now the downshift solenoid will remain disconnected, but will be replaced after I get back from the Louisville GN. 

The solenoid I believe is still available new, I also have a few extras. 
But this does not sound right, disconnecting the kickdown wire
will remove any 12V, you say it drives OK.  Connecting it should not
make any difference, because no 12V should be applied till near WOT. 
If simply connecting it DOES cause a problem, it is because the (very
unreliable) engine switch is applying 12V when it should not, repair
the switch, not the trans.  Bruce Roe

67_Eldo

I agree with Bruce: the switch must have flaked out. It's not surprising. That area gets mighty hot and the original switch design is not the greatest.

In my case, I replaced the original switch with two components:

1. Bruce's switch-pitch controller box.
2. A universal THM400 kickdown switch from B&M (https://www.summitracing.com/parts/bmm-20297), which is overpriced for what you get, but at least all the pieces are there. I also had to fabricate a new bracket to hold the new kickdown switch.

My solution isn't as tidy as the original layout, but it is much more adjustable.

When the only NOS original switch I could find was priced at $550, that made the decision to build my own setup much easier. :-)

Gary McKinney

Bruce is absolutely correct....  the problem is the switch.  I had time this morning to look at it, and, sure enough, the switch is sending 12v all the time to the kickdown solenoid (which is now disconnected).  So, can these switches be repaired?  I've been driving the car and it drives perfectly fine with the switch disconnected.  I had the idea to disconnect the kickdown wire and keep the switch pitch connected (as it still works OK), but don't know if this is a good idea.  Anyway, I feel OK driving it to the GN like this.

Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

Gary McKinney

Update:

I was able to locate a NOS kickdown switch (still in the original GM box!), which solved the problem.  All is well again.

Thanks to all for the helpful input.

Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

clarkent5477

Hello: I have a similar problem on my 1966 Fleetwood. I pulled away from a red light last week at about 25-50% throttle. It shifted fine from first to second, but no second to third. First, second, and reverse work fine and feel strong. I can hit the switch by the carburetor and hear the clicking. I also replaced the modulator to no avail. Shall I disconnect switch and see? Change the fluid and filter next and check the governor? Or are the symptoms revealing fried clutches? 

Thanks in advance!
Clark Dilley
Los Angeles, CA
'66 Fleetwood Brougham, '66 Fleetwood Eldorado

bcroe

Your trans shifting is a completely separate function from your switch
pitch torque converter. 

A different function is the electric kickdown, which could keep your
trans out of high gear.  Just unplug the trans and see if high comes back. 
Something else that tries to prevent upshifts is no manifold vacuum
connected to the vacuum modulator. 

For an internal fault, better get that trans fixed before more damage
is done.  If your trans is original, it is WAAAY overdue to be refreshed,
regardless of low miles.  Tell any shop you ABSOLUTELY MUST RETAIN
THE SWITCH PITCH FUNCTION, under 100, 000 miles I would reuse
the torque converter.  Not understanding, they have been known to
just throw away these parts.  good luck, Bruce Roe

clarkent5477

Thanks so much, Bruce. I will try that as a hail mary move. It is probably overdue for a refresh. If you or anyone else know of a good shop near Los Angeles, CA, I'd love to hear about them.
Clark Dilley
Los Angeles, CA
'66 Fleetwood Brougham, '66 Fleetwood Eldorado

clarkent5477

Bruce: So get this.. This afternoon I disconnected the kickdown switch by the carb and took it out for a test drive as a "hail Mary". Still no third gear.. so I'm driving down the street stuck in 2nd gear and on a hunch I switch down to D2 then back to D3..and wouldn't you know...it shifts to 3rd gear! I did this a few more times (manually shifting between D3 and D2 then back to get it to go to 3rd gear) then got on the freeway in 3rd. I drove it for about 5 minutes then got off the freeway and it's shifting into 3rd again on its own while in D3. I checked the fluid and it seemed a little high, strangely because I lost fluid after changing the modulator. First thing I'm doing after it cools off is changing the fluid and the filter. Could it be just a plugged passage in the transmission? Thanks for all the responses and support!
Clark Dilley
Los Angeles, CA
'66 Fleetwood Brougham, '66 Fleetwood Eldorado

bcroe

Not the expert here, but it sounds like the valve body is sticking.  That
might be a sign of not so pure trans fluid.  Apparently you found a way
to get the valve moving again.  It is possible to remove a valve body
without taking out the trans, a somewhat delicate and messy job. 
Bruce Roe