Need help with speedometer problem

[808countryside]

I have a 1985 720 extra cab. My speedo cable keeps on breaking 3 times already! so my mileage and speed does not work but my gas and temp gauge still works. Was thinking about getting an aftermarket speedometer but cant find one. Did anyone encounter this problem? Or installed an aftermarket speedometer what brand and model? Was it hard to install? Do I need my speedo cable to run an aftermarket speedometer? Need help!

[drumaniac3000]

I'm in the same boat except that my odo still works, but my speedo needle fell off a few years ago and the spring is messed up. Haven't found any aftermarket options, although I did see a few old clusters on ebay a while back.

[808countryside]

I was looking at the equus speedometer gauges and i think it uses the stock speedo cable but needs an adapter to plug into the gauge though. i just emailed them, so im just waiting on a response.

[Rev_D21]

If the cable keeps breaking then I don't think an aftermarket gauge is going to fix the problem. Why does the cable keep breaking? Is it binding inside the sleeve? Is it installed and routed properly? Is the driver gear working correctly? Is it the right cable for your year and model truck? Need more info on your problem before you go wasting money on something that might not fix your problem when all is said and done.

[808countryside]

got the right part number. Lubed it like it was stated. What I found strange after replacing the cable. My speedometer needle would jump up and down between 20mph to 35mph then stops jumping as I went faster. It never did that before.

[Rev_D21]

Sounds like the gear inside the transmission, the speedo drive gear, is in need of replacing.

[Davezilla]

When you change out the cable, are you changing out just the cable inside the cable or the whole thing, outer cable housing and all? From what it sounds like is it's binding or catching on something which will make it jump around at lower speeds then smooth out as the truck goes faster, then the cable is very short lived. I've had the same thing happen to me on a different car and it was the outer cable housing was worn out so it didn't matter how well the inside cable was lubed up it would fail rather quickly...

What it is is there's a teflon inner lining in the cable housing and if it wears thru (most likely at a tight bend) then there's metal to metal contact where it will heat up and once the lube is burned away the cable will twist off after only 50 miles or so, if it lasts even that long. the problem is you got 2 similar metals rubbing against eachother which will heat up ntil one or the other parts fail, if you're just changing the inside cable, check the cable housing for any tight bends or any signs of damage or crushing, or just look on the outside of the cable for signs of the outer plastic being melted or for any other obvious damage or defects.

With a new cable and it's outer housing, you want to route it so there's no tight bends and nothing in it's way that can crush the housing, a loose smooth bend won't hurt anything but a tight radius bend will cause a higher friction point where the inner cable can eat thru the teflon inner lining allowing it to run metal to metal and heat up until it distroys it's self. The same will happen if the outer housing gets crushed or kinked.