Speedometer drive gear problem?

[Pax84]

I’ve recently installed a new (rebuilt) gauge cluster and speedo cable in my bronco due to my old cluster failing. I recently went to move the truck and letting off the clutch in first gear to an idle speed, my speedo needle went crazy and even started to get hung up on certain speeds.(30,50,70, all while going slow in first gear) I then pulled the cable out of the t case and used a drill to test the cluster, with the plastic drive gear on I got the same symptoms and even had the clip fly off the drive gear. When I took the drive gear off, my cluster seemed to work smooth and fine no bouncing no hang ups and went consistent with the speed of the drill. It seems obvious but is this a failing drive gear? Or am I not assembling it correctly, I pushed it all the way down and clip it in, while in this position I would get the bad symptoms on my cluster. When I clip it further up on it shoots off.

 

[DirtDonk]

Sounds like the inner cable is slightly too long.
Or perhaps it’s not fully engaged in Speedometer itself?
Not sure how it would only go partially in though, and keep pressure on the gear at the other end.
Have you compared your gear to the ones listed for Broncos?
I believe all years of Early Broncos used only one style (Different tooth counts, but only one type), whereas Ford had four or five different versions available for different vehicles.
Even if it was in prior to this, it wouldn’t hurt to verify that it’s the correct style. Unless you are already sure.

I have heard of replacement cables being too long however. Is it an original cable by any chance? Or a replacement?

 

[Pax84]

Sorry I should have added that I’m using a 4 speed and np205 transfer case out of a 78 Ford. The drive gear itself is the yellow/gold 18 teeth plastic gear.(I’ve seen it in bronco graveyard and npd). The cable is aftermarket from wild horses the extended cable. Does this require the full size truck cable? And I feel like it should be engaged with the speedometer due to the drill test but I’m not sure.

 

[Broncobowsher]

I'm with Paul, sounds like the cable is too long and is putting a thrust load on the speedometer head.
Or it was a bad speedometer head rebuild. That does happen.
Cables are more about the right length and the right ends to attach them. Nothing special about using the truck stuff.

 

[Pax84]

Okay well I guess I’ll get another cable and see how that goes, I’m pretty confident the speedometer head is good because of the drill test I did before hand.

 

[DirtDonk]

Instead of going to the hassle of replacing the cable, why not clip a little bit of the end off? Say about 1/32 of an inch maybe?
I don’t imagine they “clip“ very easily, so maybe a file would be the best course of action.

When you push the gear on, how far is it from the clip lining up with the slot? That should be all you need.

 

[Pax84]

The clip was quite a bit a way, cut the cable down and it kind of spread out from itself. I tested it with the drill and seemed to work but after I installed it back into the truck I’ve got nothing. I’m gonna need a new cable now lol but hopefully that was my issue, definitely was too long.

 

[DirtDonk]

Yeah, sorry I forgot to mention that they can fray when you cut them down farther. But usually if you just cut a little bit of the tip off, it's not a problem.
I guess at just the tip they are pressed, or swaged is possibly the proper term? To keep them from unraveling under normal conditions.
If you go too far it starts to unravel. I didn’t think you had to go that far. Sorry about that…

Is it not usable at this point? You can’t put him back together again? As the old nursery rhyme says?

The good news is you might be able to get a universal replacement inner cable only down at your local parts store.
I’ve never bought one myself, and don’t know if they are still a thing, but have heard of plenty of people finding them in the past.

Paul

 

[Broncobowsher]

If the inner cable was too long it can wipe out the speedometer head. Thrust load.

 

[Pax84]

So would that mean my speedometer head could be damaged now? I haven't really put to much on it only moved it about 20 feet. And is this a common occurrence? Hopefully I wont be going through so many cables.

 

[Broncobowsher]

I had a local speedometer shop rebuild a mechanical tach many years ago. He was very addiment about making sure the cable wasn't too long or it could damage the rebuilt tach. 25+ years later and the tach still works.

 

[DirtDonk]

Yeah, I wouldn’t think for the minimal time you have spun the cable there would be any real damage.
I don’t really know that, of course, because I don’t know them in intimate detail. But I would say you’re OK for now.
At least don’t worry about it until you find out otherwise.

 

[Pax84]

Got a new cable and now everything is working, my Speedo is off by 10 mph(10 on speedo is actually 20 gps) but I solved the bigger issue. Guess I just got unlucky with cable lengths.