Speedometer and Gas Gauge

[T Col]

122411 - Just gave my son his first truck, 79 F150 Ranger, and of course it starts our "journey" to get this truck back to the prime of its life. Two things that I have to gifure out and wondering if anyone has thoughts

Speedometer- previous owner has changed the rear end and now the speedometer is MAJOR off; he gave me a new cable in the package that is supposed to correct it, can I just change the end or do I have to snake the whole assembly in place

Rear Gas Tank / Gauge- it still runs when I switch to this tank but the gauge goes to E, since it still runs I am wondering if there is a fuse somewhere or wiring that regulates the gauge.

 

[DNFXDLI]

I don't think changing the cable will correct a gearing change...the driven gear will have to be changed.

 

[T Col]

That is what I was asking ---- the "gear" on the end of the cable - (or is that what you are calling the driven gear?)

 

[DNFXDLI]

That is what I was asking ---- the "gear" on the end of the cable - (or is that what you are calling the driven gear?)

Yes, that gear.
http://broncograveyard.com/bronco?search=speedo+gear

The gas tank could be the sender unit, the connection or the wiring. I believe that the fuse that controls the main also controls the aux.

 

[T Col]

Thanks for the info and the website, Merry Christmas

 

[DNFXDLI]

No problem, Merry Christmas to you as well!

 

[Evan's f250]

for the rear tank, i would pull out the sending unit and move it back and forth multiple times and put it back in to see if it will work.

u can also reverse the polarity going to the sending unit, and if it goes over full, the unit is bad

 

[Mil1ion]

The issue of the fuel gauge is complex because there are so many things that can go bad

1) Float fills with fuel and stays low in tank
2) Variable resister that no longer works
3) Bad ground of the SU to tank to ground of truck
4) Bad connection at fuel divertor

The usual cause is Bad ground of the SU to tank to wiring to frame
Usually a great clean up and resecuring the ground fixes it

 

[Mil1ion]

Tire size / Rear axle ratio determines which driven gear to use

If they aren't STOCK tires and rims it will be more difficult to determine.

Please post all the pertinent info so we can get you the correct driven gear to use.

The original size of tire was L70R-15 - (approximately a 29.7 " tire)

Normally today a P235-R75-15 is the replacement

 

[T Col]

Thanks for all the info- if the weather holds we will be under the truck digging around tomorrow

 

[T Col]

Well, the weather did not hold and I don't have all the requested information but after getting buffaloed over the speedometer cable that the previous owner left me not looking like what I thought it should (not being able to hook it up like it thought) and the "box" that the cable went to and then out to the panel. So, I think that I have figured out that this is the cruise control box but it still does not tell me why the cable looks like it does - I am tempted to break into this box- is this where I will find the gears that need to be swapped? I googled and found a cable that looks just like the one I have but I sure can not figure out how it is to hook up (the connectors simply are not the same),,,,,, is there an adapter that I need to be looking for? TERRIBLY CONFUSED any support or encouragement is appreciated.

 

[Mil1ion]

The driven gear is located at the transmission end of the speedo cable. You need a 10MM wrench to loosen the bolt and pull the cable out to replace the driven gear.
They are color coded to show how many splines are on each one. These splines are what causes the speedo cable to turn a certain speed.
16 spline on the left > 21 Spline on the right

http://www.transmissioncenter.net/speedometer_calibration_______va.htm#Older_Ford

There isn't any box for OEM speed control Speedometer CABLE



There is a speed-sensor that 2 cables attach to that senses the spin of the cable sending a signal to the black box that the HARNESS plugs into.

 

[Mil1ion]

 

[T Col]

Thanks for the pics and the diagram Mil1ion - I looked for hours on the web trying to find those diagrams and never could - where did you get those?????

Anyway, your diagrams show what I was kind of expecting to see instead of what I found. If you come out of the speedometer and travel to the front of the truck the cable goes into a black box, not electronic, appears mechanical (still for one more day resisted the urge to take the box apart, got distracted). I say it is mechanical because there are no wires going to it, only the cable from the instrument panel (upper I assume) and then another going down to the tranny (lower I would guess).

The cable the former owner gave me, C3011A comes back to this truck, however one end looks like it could go to the tranny (but now that I see your diagram possibly to the speed sensor that I do not find (unless it is in the mystery box)) but there is a big chrome end that "could" I guess if you hold your mouth right go to the instrument panel.

A better question from reading your data and my own research is the actual gear, (color coded change out) if I take the cable loose from the tranny is it small enough to pull out or do I have to disassemble the tranny to get to it???? And my curiosity about the mystery box I have been talking about on the front driver fender under the hood,,,,,, could they by chance (hopefully) be doing conversions with these gears inside of this box since I can not find any electrical wires going to it that would make me think cruise control?

Thanks again for everything

 

[Mil1ion]

I have spent thousands of $$$$$ building my automotive library and also received a few things from former Ford Truck enthusiasts

 

[Mil1ion]

Probably an aftermarket speed control

Saying "Cruise" is the wrong terminology.

It should have never been called cruise control.

 

[Mil1ion]

 

[DNFXDLI]

You can buy the Ford shop manual on a CD

 

[T Col]

Gentlemen, how very embarrassing - it is amazing how having the thermometer up to a decent temperature, sun shining, and plenty of light improves things.

First of all, I traced the wrong cable from the tranny to the wrong location, but with all the above and the diagrams I have figured out that the previous owner left me with the wrong cable as it goes straight from the tranny to the panel

The mystery box, (don't know what it should be called) probably with what I know now does something with the cruise control (as I can say know i found all the wiring) So that I can do my part for your library I am going to take pics of all of this and let you file them away (which I have started just don't know how to put a picture into this) (it does not like my iPad)

I now know that (I think) need a CA3015 cable (and or figure out what the new rearend is from a lightning (awful low, maybe a 4:11) so I can get the needed internal gear

Thanks again, I will get these pics to you so you can have it to go along with your other diagrams as it is close but different

 

[Mil1ion]

It appears I forgot to post this as well