Backup light switch for transmission?

[Matthew Ziegler]

switch

maine, yes i'm referring to the rubber boot for the ford, actuator is a solenoid like gizmo that makes the power locks go up and down. The switch i used can also be found in any junkyard it's plated steel, 2 inches long it resembles a 5/16-18 bolt drilled through with a spring loaded plunger extending past the bolt head should be one on almost any 80's car or truck. while the powerwagon may be different, it was very easy to do with the trans in the truck on my m37 after removing the transmission cover and the gear shift. drill a 3/16 hole in the freeze plug, pry it out with a straight punch, clean the hole out with a wire brush, the ones you use for cleaning copper plumbing fittings work well. once it's nice and clean, use a 3/8 inch drive 1/2 inch deep socket to drive in the machined plug. make sure the switch is already in the plug and secure it with either a drop of loctite or add a lamb nut to the back, this is outside the trans.
MY e mail is mattrziegler@gmail.com e mail me and i'll send you a picture or two.

[maineSS]

I was able to find a book at NAPA to look thru, complete with pics. I found at least 10 likely looking candidates from the 80's-90's era U.S. cars and trucks, but the store only had two of these on hand. I went with the more compact of the two- NAPA#DJ6130 at $6.75.

It's about 2 1/2" long overall, with about 1 1/8" being the metal body(Pic #1). The body is ~ 3/8" dia, and would need about 11/16" from the face of your brass plug to allow the plunger to fully open. It has a total plunger movement of 1/4", but is "off" after about 1/16" travel in.

I'm thinking there must be a socket these fit into, as the switch assembly rotates freely in the housing, allowing the body to be screwed in/out of the doorframe.

Maybe you could get a free 1 -yr PWA subscription by doing an in depth article for Gordon- this is something a lot of people have thought about over the years, but most assumed it needed a special switch custom made for transmissions.

[Matthew Ziegler]

looks good

maine, the switch I have is 17/8 long with almost 7/16 of plunger sticking out, yours looks like it will work fine, you may want to make a thinner 3/4 inch plug, this will allow some of the switch's threads to protrude. by doing so the depth of the switch into the trans is easily adjustable and you can lock it with a simple jamb nut. while I had the adaptor in the lathe, I cut a shallow groove in the area that will protrude from the trans with a parting tool, this gives you something to pry off of with a small bar or screwdriver in case you ever need to remove the switch assy. I'm considering the article idea or selling kits, they're not very hard to make. I try to go for factory looking modifications, seen too much torch cut angle iron and duct tape buchery. coming soon, m37 windshield washers these will be a stock looking bolt on setup. I just got a picture of my setup, if you e mail me i'll send it to you.

[maineSS]

Matt, is the brass plug a friction fit in the tranny case, or is it threaded in? I was thinking from your earlier description it was threaded (which is why I thought you had done it during a tranny rebuild).

If these have a socket assembly in the doorframe, that might protect the contacts & backside along with providing a convenient way to wire it up. Hopefully it's not an OEM-only thing.

I noticed on mine that the contacts are separated from each other by the plastic strip and collar assembly- when they touch the base of the plunger, current flows thru the metal part of the switch, and anything else it's attached to. Looks like it has to be a Ground circuit.

One of the advantages of having this is if you later install the Dennan overdrive unit, you can wire this into the control circuit and avoid making a $1300 Ooops! by shifting into reverse with the Dennan still engaged.

[Matthew Ziegler]

plug

The plug is pressed in. After you remove the freeze plug from your trans you'll notice that the hole is stepped, that is the outermost 1/8 or 3/16 is 3/4" in diameter after that it is of a smaller diameter. This is to prevent the freeze plug from being driven in too deep which would screw up your shifter operation. The brass plug or adaptor doesn't really extend into the trans very far. you have to drive it in with the switch already installed, use a 3/8 drive deep socket for as a punch. adjust your switch by threading it into or out of the adaptor by turning the threaded end with a pair of pliers when the contact (rearmost part where you connect the wire) is at least 1/8" away from the part protruding from the adaptor, add a jamb nut to lock it in place. If the switch you bought does not self ground simply connect one contact to one of the top cover bolts with a short length of wire, you can easily piggyback this ground to two relays which should solve your overdrive dilema I would check the switch with a cont. tester to see what it's up to

[maineSS]

Matt- is the rail used only for reverse, or does it also it get used for other gears?

I took a look at Backup Light/Neutral Safety switches in the NAPA book also.
Most of the plunger type switches are for Japanese/foreign cars, and thread into the tranny case. The big question with these is how deep the rail is in the tranny case, and what dia the switch is. They do come with a wire pigtail & plug. Most are also special order only, which means you'd better be sure about these things, because you're a proud owner once it comes in.

I asked VPW about the later PW's having backup lights- they said they had them, but didn't know if they were automatic, or manually actuated. Maybe Clint Dixon could illuminate this dark corner of Flat Fender history for us?

[Matthew Ziegler]

rail

Maine, that rod only moves when you put the truck into reverse. when the truck is in neutral or any other gear the rod is about .500 away from the freeze plug, when you put it in reverse it goes in more, at least another 3/8" this is what I can tell from a trans I took out of my parts truck, yours may differ slightly. the outer bore is .750 where the plug goes in is roughly .160 deep, then the hole steps down to .687 or 11/16. I would use the door jamb switch, the one in my m37 is working fine, there are no internal springs or contacts to get wet or messed up, just one moving part and it'll probably never be obsolete as far as availability.

[Clint Dixon]

Matt- is the rail used only for reverse, or does it also it get used for other gears?

I took a look at Backup Light/Neutral Safety switches in the NAPA book also.
Most of the plunger type switches are for Japanese/foreign cars, and thread into the tranny case. The big question with these is how deep the rail is in the tranny case, and what dia the switch is. They do come with a wire pigtail & plug. Most are also special order only, which means you'd better be sure about these things, because you're a proud owner once it comes in.

I asked VPW about the later PW's having backup lights- they said they had them, but didn't know if they were automatic, or manually actuated. Maybe Clint Dixon could illuminate this dark corner of Flat Fender history for us?

I have never owned a Power Wagon new enough to have a backup light switch, except for a 1964 W200 with a NP435 transmission, so I can't really add anything to the discussion.

[maineSS]

This is proving to be more of a mystery than I thought. I expected Clint would easily ferret out the PW's backup light history from his vast collection of PW production data, but perhaps it's destined to remain obscure.

I decided to modify my switch to allow it to thread into the plug from behind. Pic #1 shows the new configuration, with the threaded bushing reversed on the plunger housing. I'll post some pics later on how this was done, as I expected to destroy the switch during my experiments, and didn't have my camera handy. I think this will make it possible to use switches whose plungers might otherwise be too long, as threading the switch in from the front limits plunger length to ~ .500 in when fully collapsed. Also, you can more conveniently set plunger depth, since the bushing head is accessible, and can be turned in/out with the wires hooked up.

[Tom Petroff]

FYI,
Hopefully your aware that the switch your trying to use is "Dome/Courtesy"light door jamb switch.
It is not insulated and must be used in the 'electrical Ground" Circuit.
The "68" model year WM300 used a NP420 trans. with a bullet switch in the shift tower as your trying to do.
TGP

[maineSS]

Yes, it's definitely a ground circuit- the idea being it won't draw current as long as it remains open. Was the 420 switch a screw-in or a drive in type fit in the tranny case?

[Tom Petroff]

Screwed in, on the left side of the case.
Similar to this switch.
TGP

[Clint Dixon]

This may be of help

...I expected Clint would easily ferret out the PW's backup light history from his vast collection of PW production data, but perhaps it's destined to remain obscure...

I was able to find some parts numbers in the May 1969 parts list 81-690-0817, and ONLY that list. I do not have the earlier list dated June 1968 that this one supersedes.

The part number for the back-up lamp switch for the WM300 model after serial number 1668000 is 2258 404. This was used on the WM's 420 model transmission of course. This same part number shows up as being used on some of the A100, D-P-W100 and 200 models with the LoadFlite transmission, the D-P300 models with the 435 transmission, the 400-500-600 trucks (no model designated), and the D-C700 thru 1000 models with the 540 and 541 transmissions. There are no images for any of these applications.

[maineSS]

Clint- 2258 404 is still a valid PN. I ordered one in from NAPA to look at, should be in tomorrow.

[maineSS]

Here's a pic and some dimensions for 2258 404, NAPA Part No. NS5671.

The dia of the boss just before the threads is .865", boss length is .185".

The dia over the threads is .555", .610" over the O-ring.

Length of the threaded part over the ball is .425", length including the boss is .510".

The ball has to be depressed about 1/16" to make contact and allow current flow. This means it would have to be mounted on the front rail plug of the crashbox so it could be depressed as you shift into reverse (assuming the dimensions allow it to fit). Cost was $14.99.

Tom- where is the switch mounted on the 420- left front or rear?