Backup light switch for transmission?

[maineSS]

I was looking at a diagram for the PW tranny, and wondering if the rails are stationary or fixed in place. If they move in the case, then it seems a momentary off/on switch could be fitted for reverse so you could have backup lights. Anyone diassembled a crashbox lately?

[mannyc]

shift rods

i believe that the rods move back and forth in their bores. i also believe that some have 'caps' or plugs at the back of their respective bores. anyway, i think that you could thread the appropriate bore in back of the shift cover to accept a plug to hold plunger type switch. i wanted to do it on my m37 but never got around to it.

[Jerry Henry]

What I want to know is, why didn't Dodge provide a back up light switch in the first place? Oh, wait, they didn't provide back up lights, either! Now, what were they thinking, I'm supposed to back up my truck, with the plow attached to the rear, in the middle of the field, in the dark.......? How thoughtless of them. Ha Ha. I'm just kidding, here. I have thought of how I could install a back up switch on my W300 as well. Flipping a little toggle switch to turn the lights on is not so hard, remembering to turn it off is the problem. I wonder if anyone makes a "time release" toggle switch, for us old guys with memory fatigue?

[MoparFreak69]

Here is a simple suggestion to try. Why not place a micro switch at the base of the shifter. Position it so that it is only engaged when the shifter is placed in reverse. Have the micro switch power a relay so you dont burn it out trying to power lamps. Im sure you could fab up a quick and easy bracket as it wouldnt be holding much weight and definately wont have much force on it. That is how bobcat engages their back-up alarms as the hydrostatic drive has no other way of telling which way you are going.

[maineSS]

I've thought of putting a switch on the shift lever below the knob, and of mounting it at the base of the lever. 4th gear and Reverse are pretty close together at the base of the lever, it just tilts over a little, not much actual displacement. Mounting it under the knob is doable, but you'd likely forget it's on unless you wire it to an alarm, or make it momentary "on" in operation, which means holding onto the gear shift as you're twisting round to see what's behind you. That's probably why the OEM's use the internal transmission switch. If the rails move in the case, then replacing one of the plugs with a switch would be the way to go, assuming 4th and Reverse don't use the same rail...

[Don Williams]

I have auxiliary backup lights on one of my trucks. I mounted two lights and each one has a 55 watt halogen lamp which is far superior to any factory backup light I have ever used. These are a common item at most any auto supply or accessory store.

I have a toggle switch on the dash which controls a relay that carries the load of the lights. There is also a small pilot light above the switch to remind me the lights are on. The switch is wired so that it only has power to it with the ignition switch in the "ON" or "ACC" position. I sometimes use the lights while working behind the truck at night and having them work in the "ACC" position is great for that.

When I back up at night time I turn on the lights, the sun rises behind my truck, I safely back up, turn the lights off, and go on my way. If I'm backing up to park I sometimes shut off the ignition switch before turning off the backup lights. This shuts the backup lights off as well. Next morning when I crank the truck the pilot light is there to remind me to turn the backup lights off. Three years later I have yet to forget and drive down the road with them on but I know the day is coming.

The talk of a timer here got me to thinking and I found the link to this little timer. I'm thinking of using one of these with a 3-position switch to control the backup light relay. Switch positions being (1) center off (2) spring return up momentary on (3) down constant on. The momentary switch position could be used to control the backup lights via timer, constant on switch position could bypass the timer and power the lights until turned off.


http://www.altronix.com/index.php?pid=2&model_num=6062

[Doc Dave]

I took an old dash light switch correct for the PW, and rewired it for two backup lights I sourced from CarQuest, that are round and rubber encased. This style is often seen on farm tractors at the back.
When I need to back up, I simply pull this switch which I mounted to the left side of the steering column.
I am not sure if the amount of juice running through the switch is a bad thing or not. Should I use a relay?
I can post pics if interested.

[MoparFreak69]

I've thought of putting a switch on the shift lever below the knob, and of mounting it at the base of the lever. 4th gear and Reverse are pretty close together at the base of the lever, it just tilts over a little, not much actual displacement.

Thats why I suggested a micro switch. When properly set up they take only a couple thousands to go from engaged to disengaged. You just set it up so that when you are all the way over to reverse its engaged, but when in fourth it doesnt engage. They are fairly cheap ($20 +/-) and very reliable. They are used in a lot of heavy equipment for just the purpose you mentioned.

Here are several different options in one place
http://www.surplussales.com/Switches/SWPressMic-4.html

[maineSS]

The other problem with a microswitch at the base of the gearshift lever is exposure- to booted feet, lots of dirt and moisture, and wide temperature swings. Most microswitches are meant for indoor use in a protected location for line voltage/low amp uses. I'm thinking the Bobcat switch is a special unit- with a special price to match.

[NNICKB]

Later FFPWs had backup lights. You might be able to retrofit them.

[maineSS]

I expect those might be the WM300's of the 1960's- it would be interesting to see how backup lights were done.

[Matthew Ziegler]

switch

Maine, I successfully put a switch in my m37 trans, remove the left rear closest to the driver freeze plug from the top cover. This is the reverse rod, when you shift into reverse it moves in. I had a working setup with a bracket, seal and plunger activated micro switch, however I ran into clearence issues with the floor pan when i re installed it. The new version is a 5/8 inch long chunk of 3/4 inch brass round stock drilled and tapped in a lathe to 5/16 18. threaded in and sticking out the back is a regular $2 door jamb switch from pepboys. The brass takes the place of the freeze plug, the switch is cheaper and more reliable than a normally closed micro switch. Wire it so the jamb switch grounds the coil on your relay, connect your two remaining hots to a convenient fused power source and switched power to the reverse lights. It's wise to buy a 5 terminal relay, this allows you to install a toggle or rocker switch giving you the option of rear lights without putting the truck in reverse. Very handy for hooking up trailers or offroad recovery,

[maineSS]

Matt- I assume your M37 has the 4 spd box, but is it late or early (mine is early). I haven't checked the exploded diagrams to see if the later boxes have the same internal rail setup. There was a "late crashbox" before the semi-synchro unit, do you know what's in your truck?

From your description, I'm imagining that the brass plug is tapped into the freeze plug hole in the case, and the switch contacts the back of the rail when you're in one of the forward gears or neutral. In reverse, the rail moves forward, and the switch allows current to flow to the relay/backup lights, correct?

Does hot tranny oil kill the doorswitch over time? Your mod is progress in the right direction. One of the things I want to do is alert other traffic when I'm backing up- it's been so long since automatic backup lights were introduced that most drivers won't notice you're reversing til you actually hit them.

[Matthew Ziegler]

backup

yes, all the switch does is supply the relay with ground. the switch i used is plated steel, only the end where you attatch the wire is insulated, also due to the location, very little oil winds up there. so it should have no ill effects on on the switch. i'm considering the addition of a rubber boot over the device to protect it from dirt etc. I found one off of a late model ford van power door lock actuator that should fit the bill. as long as your truck shares the same shift pattern as mine this will work, I recently rebuilt a 42 ford crash box and the topcovers and shift rods operate the same way.

[maineSS]

I dug out exploded pics of the "up to", "after" and semi-synchro boxes- the two crashboxes have the same rail pattern, but it looks like the synchro box is different.

I went down to AutoZone and Advance to look at door switches- there's a variety of these, some of which are not suitable, being plastic and large in size. I intend to try NAPA, hopefully they'll have a catalog I can look thru, instead of a teenager behind a computer asking for model/year of vehicle.

Does the "late model Ford door lock actuator" refer to a switch possibility or the boot? I assume you did your mod with the tranny out of the truck?