I just finished restoring my 77 F250 CS and I added OEM A/C. I took the dash apart to include the speedo being disconnected. The speedo now starts off at the bottom right (80mph) about 5 o'clock and moves toward the left as i speed up. It seems to work fine other than starting off being at 5 o'clock (80) instead of 7 o'clock (0). A) what have I done and B) what can I do to fix it? Thank you to any other forward thinking but backward acting drivers out there. Jack

 

Is there a post the needle sits on at 0 that could be missing?
I just looked ay my 81 speedo picture and don't see a pin so maybe not?
I have had mine in and out a few times along with other makes and never had thatissue.
Good luck on a fix.
Dave ----

 

So by moving to the left, you mean that it still rotates in the correct direction (clockwise) as before? Just starts off at the wrong location?
Sounds like it got bumped past it's zero stop, or the needle itself got rotated slightly. I thought the old speedos had a stop pin/post/thingy, but I'm not out at my truck to look at the moment.

Either way, I'm pretty sure it's not the cable being removed temporarily that caused the problem. Had to be something happening while it was out.
Does your cable have the "unscrew" type metal bezel, or is it the "finger squeeze" plastic type? Been a long time since I've been back behind the dash.

Good luck.

Paul

 

My advice is to disconnect the cable and note where your needle sits. The speedo cable is just a flat slot that plugs into the back of the dash, with a screw collar to keep it in place - unless Ford made more than one type of setup. I've had mine apart a handful of times and I recommend taking care not to damage the collar (mine is brittle). You can remove the cable without disassembling anything, assuming you don't have Hulk Hogan arms. If your needle doesn't sit where it should once disconnected, you know where your problem is. Let us know what you discover and we'll see what we can recommend further.
- IH

 

those are able to just gently rotate the needle around to obtain the stop you need for proper calibration. Remove the clear cover, that you look through while driving, and grab the needle gently and rotate the needle. It will reach a stop in the direction you want it to be corrected, and just rotate it until it lines up with 0 no external stops that I have ever seen.

 

IH,
Thanks for the reply. So I am clear, I can go under the dash while getting myself into some sort of yoga position and unscrew the collar and simply pull out the cable. Once the cable is pulled out, the needle should go back to 0 from where it sits now at 85? And if it does go back to 0 then just reinsert the cable and hand tighten the collar again. Then if the needle does nothing then....buy a Silverado? Thanks for the input and sorryif I sound dense but I am new this area. Jack

 

Yes Jack, you should be able to stand outside your door and reach your arm up to feel where the cable inserts into the back of the dash. It only takes a half-dozen or less half-turns to release the collar down the cable - then gently back the cable off of the speedo unit. I don't know about moving the needle manually as WH suggests; I was just trying to eliminate the source. I assume if the needle moves to 0 once the cable is out that you may have solved your problems. Dunno nuthin' 'bout no bow-tie trucks except their weak-*** 10 and 12 bolt rear ends - and who puts the dizzy in the back where you cannot work on it easy enough?!
- IH

 

IH probably has more info, but definitely a 10-4 on that yoga position (multiples in fact, until you find one that does not cut off blood flow to the brain) and unscrew the collar.
But if I remember not every vehicle is cooperative with regard to pulling the cable out. Some are anchored in the firewall so tight that the VERY stiff cable does not always cooperate. That's been my experience anyway.
But they all eventually come out. Even the tough ones. I've never had to remove the instrument cluster just to get the cable to come out of the speedometer head, but I was this close to needing to a couple of times, with different vehicles.

You will know what type of retainer you have as soon as you reach up behind the speedo. It'll either be a small round knurled collar you simply unscrew (most older American vehicles) or a plastic clippy-doodle thingy where you squeeze two ears and pull away from the speedometer hub.

Only if the cable is what's jamming it up. It's common for them to jam up on the drive nub sticking out the back when installed crooked, but in those cases the needle would normally not move at all when driving. And yours sounds like it's still free moving because you get a change when you're driving.
If you're lucky, you'll see it just release when you pull the cable. I'm not betting on it yet though.

hah! Good thought. I have a mostly bare bones 2019 Silverado and love it! Not embarrassed to admit that I love my '79 F350 and my Broncos, but thoroughly enjoyed my '96 K1500 and now my new one even more perhaps.
The killer gas mileage does not hurt those feelings...

But if it does nothing, then I would pull the cluster out like suggested (or just the clear cover if that's doable) and then manipulate the needle. Regarding that, all I know is you have to be delicate and super careful not to force something.
Some speedometers won't let you turn the needle alone because the mechanism behind it just spins with it. If you can do this though, that would be fantastic.

I'm sure there are tutorials on speedometer maintenance, but in case you're not aware there is no physical link between the cable and the needle. The cable spins in the hub, turning not only the directly driven gears for the odometer mechanism, but also spins a magnet attached to the shaft, around which sits a lightweight metal "cup" or sorts. The needle's shaft and the needle are attached to this cup and have a little tension on them by a clockspring to keep it from just bouncing crazy like and put just enough tension on it in order to fine-tune how much the magnet makes the needle move for a given number of rpm.
It's a simple mechanism. Honestly though, I'm totally spoiled by modern electronic speedos! Just unplug the wires and replace the whole thing if it goes bad.

Probably didn't need to know that, and hopefully I did not get anything too far wrong!

Good luck.

Paul

 

Better clocks' hands are actually an indicator arm affixed to a center hub. You regulate the exact minute the hand points to (for instance when it chimes) by removing the hand, placing a small tool in the center of the hub and rotating the hand until it's correct. It would be nice for a speedo needle to be similarly adjustable so if it read 'off' you could adjust it to indicate the correct speed?