1950s trunk pull downs

[Lars Kneller 8246]

What years were the first generation electric trunk pull-downs used? 1955 to 196?. I know they switched to a hydraulic unit in the 60s sometime. Thanks.

[Clewisiii]

Electric for 61

[Dave Ventresca]

first year was 56

[Lexi]

first year was 56

1956 was the first full year the option was offered, though many are unaware that it was first introduced late in the 1955 model year. Cadillac General Service Letter #882, dated July 28th 1955, provided details on the new "Remote Control Deck Lid Lock". The August 1955 Cadillac Serviceman also provided an introduction of this unit to service personnel, as it was then "...made available for 1955 Cadillac cars now in production". These early units were electric, but not sure when the change Lars noted took place. Clay/Lexi

[59-in-pieces]

Why would there have been a need to switch from electric to hydraulic.

Have fun,
Steve B.

[TJ Hopland]

Anyone have any pics or diagrams of this original system?  Was it just super complicated and expensive?  Was it reliable?  Was it easy to damage if you slammed the trunk?

The hydraulic one I would imagine wasn't too expensive. I'm sure there was some expense in the shock thing but I would imagine it shared tooling and machines with regular shocks which were fairly cheap and mass produced so at scale probably pretty cheap and the rest of the mechanism wasn't very complex so I would also imagine not too expensive to produce and install.  Also seemed pretty reliable and hard to damage even as they aged.   

[Clewisiii]

Here is my electronic trunk pull down, and power trunk opener.

I have not touched these, and will not until after paint and body work. So I cannot speak on condition or complexity.

[Eric DeVirgilis CLC# 8621]

Trunk pulldown mechanisms were electromechanical from 1956 (or late '55) until 1961. From 1962 to 1973 the system was clockwork mechanical without any electrical parts. The physical motion of lowering the decklid energized a spring that powered the closing mechanism. From 1974 & later, they returned to electromechanical. None were ever hydraulic.

[TJ Hopland]

Is the clockwork mechanism look like a shock?  That's what I was assuming was what was being referred to as the hydraulic system and I was assuming the shock looking thing had the hydraulic part so that was why it was named that.  I have never had any reason to look that close over in that corner of the trunk other than to watch for the arm to come back up if you missed the first try. Maybe it doesn't even look like a shock, I will have to go out and look closer later today.   

The 74-78?  Style IIRC had a crank sort of mechanism?  It was kinda like a windshield wiper motor with the crank arm that attached to the latch?   Then 79 till into the 90's? Was that mostly plastic housing system overall similar in concept to the one posted above just much smaller and plastic.

[Lexi]

I got a diagram somewhere here for it. Will look for and post if found. I think 1955 and 1956 are the same, with 1957 being different. 1958 might also be different as I remember rebuilder Jay Brown telling me that the most easily damaged unit was the 1958 one. Very easy to burn out, even when new and without much use. Be mindful of a very short duty cycle using them especially the '58.  Don't know if that was because it was different from 1957, or the same but made from cheaper materials. Brown advised that they can even burn out with just one improper use. So, be forewarned. Also, slaming the trunk closed is not good. Aside from metal fatigue, that can do a number on them. Why even have a pull down motor if you are going to slam the trunk shut anyways? Personally, a near useless accessory but the red dash light is geeky awesome.

The 1955 installed units must be rare as I have only seen one once. Lou Commisso also posted a photo of one in the old Mid-Century Cadillac Forum, just because they are so seldom seen. They are also uncommon in 1956 to see, but not as odd as seeing one in a '55 Caddy.

Attached are 2 photos: 1) the shot Lou posted years ago of the red trunk open warning light in a 1955 Cadillac. This car was obviously equipped with the trunk solenoid and closing mechanism. Note the position of the warning light in relation to the headlight switch. 2) My '56 Limo has the electric trunk optional opener solenoid and closing pull down motor. Note the position of the dash warning light here. Slightly different than the '55 placement. Don't think this was because of Dealership installation, as I believe these units were factory installs for a number of reasons. Wiring harness and I believe a bolstered trunk valance. Welding needed to retrofit to a non-factory equipped car. Who wants to do a repaint there? Not me. This topic came up on the old Forum and the general consensus was that this was a factory install. Somewhere I think I still have a shot showing the cowl plate accessory letter for the '55. Think it was "S", but not 100% certain without looking it up. Clay/Lexi

[J. Gomez]

The trunk pull-down with the solenoid opener options was available from 1955-1961 as Eric, Carl and Clay pointed out above, these units can be found under section 31.4950 listed in the MPL through years 1959. Clay you are correct on your post the option is listed/tagged as "S".   

The 1955-1957 were similar arrangement with the exception of the 1957 with a slimmer body and a new trigger switch (micro-switch style). One of the main issues with these units specially on the 1955-1956 is the trigger switch melting the cover plastic or burned contacts as these were inside the plastic cover, the micro switch also suffer the same but it can be replace (micro switch 1TB1-3 but very $$$) as a unit.

These also suffer from other broken/bend frames do to slamming the trunk while closing, I had worked on two units that had the top ears bent and/or crack striker frame.

Since the trigger switch has to carry a heavy load (especially during the pull-down trunk closing) for the motor and to save the switch from this heavy load I've added a relay. The wiring needed to be change so the relay now performs the function for the heavy load to the motor and now the trigger switch just drives the relay.

You can see the relay inside the frame with the wiring modification on the attached document I did when I rebuild both of my units (working and spare). Enjoy 

HTH

[TJ Hopland]

I would not think if everything is working correctly that the switch (or motor) should be that stressed but I could see possible issues with the alignment being sensitive and at times the motor may not be shutting off at the right time.  If the motor was stuck but still getting power then that would stress the heck out of the switch and motor.  Perhaps the reason there were so many changes is they were trying to find a design that had a little more leeway in the design so it was less likely to get in that situation.  Maybe one slam whacked something and causes the motor to run a little too long?

I did go look at my 73 and I have no idea why I thought it was some sort of shock, can't really see anything but the arm where it rides on that cam on the hinge, its got the carpeted cardboard around it. I don't ever recall having to mess with it but it seems like I'm not the only one that thinks its got some hydraulic component.

[The Tassie Devil(le)]

G'day TJ,

This is what the "Hydraulic) pull-down looks like.

Granted, it does look like it could be a Hydraulic piece, but I would hazard a guess that it is spring-loaded, with a slow-release plunger valve to pull the body upwards.

One day, when mine dies, I will cut it to pieces and investigate.

Bruce.

[J. Gomez]

I would not think if everything is working correctly that the switch (or motor) should be that stressed but I could see possible issues with the alignment being sensitive and at times the motor may not be shutting off at the right time.  If the motor was stuck but still getting power then that would stress the heck out of the switch and motor.  Perhaps the reason there were so many changes is they were trying to find a design that had a little more leeway in the design so it was less likely to get in that situation.  Maybe one slam whacked something and causes the motor to run a little too long?
 

TJ,

On these early units there is a second switch "plunger" which its main function is to switch the connection to the motor during each up or down operation, this one is a heavy duty type with a larger slider contacts (you can see them under Fig. 2 in my attach document).

The motor (trunk open) will move the striker assembly up about 1" or so and it then stops, (the plunger switch is now reversed for the closing) when you close the trunk the motor pulls down (again just bout 1") to close the trunk (now the plunger switch reverses for the opening). 

The trigger switch is the one that switches the +12V between these steps to the plunger switch input. The issue is either the older style switch ('55-'56) or the micro switch ('57) are way underrated to carry the heavy load for the motor.

I can't speak on the later units if GM changed the electrical design of the switch with beefier ones, I would guess the design changes made was to accommodate the new trunks layout to fit these units.    

[J. Gomez]

G'day TJ,

This is what the "Hydraulic) pull-down looks like.

Granted, it does look like it could be a Hydraulic piece, but I would hazard a guess that it is spring-loaded, with a slow-release plunger valve to pull the body upwards.

One day, when mine dies, I will cut it to pieces and investigate.

Bruce.

Bruce,

That one looks to be a close resemblance of the old screen/storm door closers which are spring loaded.   

I would guess there is an electrical motor somewhere to pull down on the cable during closing (soft closing) and releases during opening (pulled by the spring load inside) while the trunk raises (soft open).    

Very interesting design..!