Backup light challenge

[Thomba48]

Hi,

was wondering - being a gadget freak - I actually installed a nice (not mopar - but still nice) vintage backup light on my 1948 Plymouth business coupe. Now obviously any devices installed should also work properly.

First attempt - purchased a small hook which is attached to the gear lever strings inside the engine area. The right attachment should engage the backup light when put into the rear gear (and back). Overall, however, almost impossible to adjust. So I skipped that idea.

Of course I could install a normal switch which I could engage manually - on/ off. But that is somehow boring.

Now, what could one do (without having studied electronic engineering) to somehow install a lever device inside the dash board area that basically activates the backup light when I put the gear into reverse, deactivates it when I change the gear again?

Any ideas are more than welcomed?

Thanks/ Thom

[greg g]

Isn't there a casting on the transmission that accepts a switch for a back up light switch?

If not perhaps you could rig up an aftermarket brake lamp switch to react to the selector lever positions on the transmission,or where the sift linkage rods meet the assembly on the steering column.

[thrashingcows]

This info is from the "Brake light switch" thread.

Blueskies posted a pic of the brake switch on his car. Aftermarket lever activated switch.

And he also posted a link to an item from speedway motors....

http://www.speedwaymotors.com/Universal-Mechanical-Brake-Light-Switch,1972.html

Edited February 7, 2010 by thrashingcows

[jd52cranbrook]

Should be a back up set up already on the tranny. A bung with a receiver for two wires, it grounds when in reverse and completes the circuit. Set up mine that way. Same side as the speedo hook up.

[Thomba48]

Hi guys,

how could one adapt the lever idea (originally set-up for the break pedal) to the backup light issue.

The lever would need to be somehow "touched" by the gear shifter?

The tranny idea sounds intruiging - would need to look and check if that is in place in my car.

Thom

[41/53dodges]

are these backup light switches in the tranny on the pilothouse trucks, too?

[jd52cranbrook]

That I am not sure of, I have not seen a truck transmission.

[DonaldSmith]

I added a backup light to my 47 DeSoto. I think the transmissions of that vintage do not have a place to mount a backup light switch. So I was looking for a mechanical switch to mount at the linkage. I don't think a mechanical brake light switch would work.

The typical mechanical brake light swith is NC, that is normally closed. The brake pedal in its usual position keeps the contacts open. As soon as the pedal lever moves away from the switch, the circuit closes, turning on the brake lights. I figure that a backup light switch would have to be NO, normally open. so that movement of the the shifting linkage would push it closed.

So I bought a switch from McMaster Carr to mount under the hood at the shifting levers. It's a 7090K38, snap acting switch. It has a lever with a roller on one end. And the important thing, it's SPDT, single pole double throw, with both NO and NC posts.

I'll have to mount my switch on or near the steering column under the hood, so that when the gearshift lever is in the Reverse position, and the linkage is pulled closer to the firewall and up, it will contact the switch, making the NO circuit close.

I also bought a toggle switch for my electric fuel pump, a 7343K28, SPDT, On-Off-(On). Center position is off. One position is constant pressure, for when I want to run the pump to prime the carburetor. The other position is constant on, in case the mechanical pump fails and I need to run the electrric pump constantly. (Of course I'll get the power from the ignition circuit so that the pump can be on only when the key is turned to the ignition position.

I'm just waiting for better weather or a burst of enthusiasm for installing these switches.

[Thomba48]

Hi Donald,

you wouldn't by any chance be able to provide me with a picture of your set-up?

Thanks/ Thom

[DonaldSmith]

No picture yet. I still have to figure out how to install the switch someday. Stay tuned.

[41/53dodges]

crap. no switch on the pilothouse.

[Dave Bohn]

My 48 D24 has the "official" Mopar accessory back up light. There is a switch that mounts under the dash that you turn on & off manually. When on, the switch knob glows red. I guess that was supposed to reminde you to turn it off. Theres a pic of the ensemble, switch, wires, light, in the front of the parts manual. BTW-When I got my OD transmission from George Asche he mentioned that the 48 tranny did not have a mounting for a back up switch - the later trans do.

[blueskies]

Here's a couple of pics...

The first is my '50 three speed transmission case-

(reload your browser of the pics don't show)

And the second is my '55 Dodge ovedrive case-

In the first pic you can see a large plug on the side of the case. This plug is right over the reverse/first shift rail. It is my assumption (and I may be wrong...) that this is where the back up switch screws into the transmission case. When shifted into reverse, the shift rail pushes in the button on the switch, completing the circuit for the back up light.

In the second picture, you can see that my overdrive case has the same plug... On the overdrive transmission, there is a switch on the overdrive half of the case, but it is used for the reverse lockout system, also actuated by the reverse shift rail. The reverse shift rail on the OD transmissions is much longer, and extends into the OD case.

I don't have my Plymouth repair manual handy (it's stored with my car for the winter), but another book I have, a 1950 Popular Mechanics "Manual for Plymouth Owners" shoes diagrams and photos of the transmission case without this large plug on the case.

Anyone know if these plugs are where the back up switch goes?

Pete

[Barabbas]

Hey JD where did you get the taillights? Look like a LED cluster, could sure use them on my 52 Cranbrook

[jd52cranbrook]

I talked the guys who sell the tail lights for the 46-48 Plymouths, (or Dodges, I forget which now), to sell me just the guts. Then I set them inside the lens of my 52. Work great.

Here are some pics and a vid.Tail lights

[fedoragent]

Folks,

Has anyone with a SD Club Coupe done this yet? I think I might just mount one of the backup lights to a manual switch. I only have one light and may just mount it somewhere on the rear. I haven't figured that out yet.

FG.

[littleman]

Check service manual under back-up light. Has picture where switch goes on trans. Tapped hole may not have been on pre 50's trans though.

Manual 46 to 53 pg 243

Manual 46 to 54 pg 292

Got my switch from Riddle up in WA state

AL

[fedoragent]

Check service manual under back-up light. Has picture where switch goes on trans. Tapped hole may not have been on pre 50's trans though.

Manual 46 to 53 pg 243

Manual 46 to 54 pg 292

Got my switch from Riddle up in WA state

AL

Thank you!

FG.