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| | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | Got a problem that's popped up with my speedometer earlier this week, not sure exactly what's causing it. On Monday, I noticed the speedo wasn't reading on my way home from work. It did work fine that morning. Got home, checked things over, and found a broken cable at the transmission end. I picked up a new cable yesterday, intalled it this morning. I did run it with a drill to make sure it worked, needle bounced a bit, but it held steady reading 25 mph, so I hooked it up. I did hear some slight clicking when the drill was run the opposite direction. on the way to work, the speedo wouldn't read steady any higher than 20 mph, and would bounce from 0 to about 45 before it would read steady. Got maybe a mile or so before the new cable broke. I'm thinking the speedo might be shot, what does anyone else think?
BTW, it's in my '55 3200, the speedo itself is from a '56 3600.
Bill Burmeister
| | | | | Joined: Jul 2001 Posts: 3,887 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Jul 2001 Posts: 3,887 | jumpy needle = dirty cable housing, but assuming you replaced that as well as the inner cable, the speedo head would be gummed up - if it's moving it's fixable, just need to open it up and look, could be the gears that drive the odo
Bill | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | That's the direction I was thinking, something on odometer drive. The cable was completely replaced, housing and inner cable. I replaced both because I suspected an issue with the housing. Starting to look like I'm going to have a project for vacation next week!  
Bill Burmeister
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | It does not seem to make sense that a binding speedo mechanism/gear would be stronger than cable so as to break cable. It seems like speedo gears/mechanisms would be striped and damaged by this event. If you ran it with drill and no problem and then it broke after install, it seems like the install does it. I am not sure. Just curious, did the broken cable have a twisting look to it near the brake or at other places? or just a snap off look? or can't tell? Can't see it breaking two cables and still function with drill. Breaking at tranny end is a clue.(you did not say if it broke at same place) Did you just install exhaust or some other component and "reroute/streatch" cable in a tighter bend? Is this post just for guys named Bill?
Bill
Last edited by bartamos; 09/15/2011 5:24 AM.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: Nov 2005 Posts: 238 Shop Shark | | Shop Shark Joined: Nov 2005 Posts: 238 | I've had this problem with a speedo cable breaking, but on an old car not a Chevy truck.
The problem turned out to be that the porous bushing on the speedometer's input shaft had dried out. The input drive on the speedo would work for a while, then the input spindle would overheat and seize, breaking the cable. By the time I came to replace the cable, the spindle and bush had cooled down and become free again.
I could only see what the problem was when I stripped the speedo down and could see that the input shaft had become discoloured from overheating. I used sewing machine oil to lubricate the speedo input bush and the problem was solved.
Stuart. | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | On the first cable, which has been on the truck for about 10 years or so, has an almost "exploded" look, for lack of a better description, to the break. It broke pretty much right at the square end in the drive gear. The new cable did have a twisted look to the break, and it broke about 3/4" up the cable from the end. The only new components installed recently are a stereo amp under the seat, plus some speaker wiring, but those are on the other side of the truck. No changes where the speedo cable runs. I did try to work some more slack in the routing, just in case it was an issue of too sharp of angles, but the original was plenty long and wasn't routed with any tight bends. Both cables (or what's left of them) do turn freely in the housings.
I did have a similar issue a few years ago with the speedo reading funny, namely the bouncing part, which lead to a broken needle. That was when I swapped it for the '56 speedo that's currently in it.
Bill Burmeister
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | Which end did it break on the second time?
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | Both broke at the transmission end.
Bill Burmeister
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | The problem turned out to be that the porous bushing on the speedometer's input shaft had dried out. The input drive on the speedo would work for a while, then the input spindle would overheat and seize, breaking the cable. I'm thinking you've hit what's wrong with mine. I finally got the speedo out of the dash today, the cable end of the drive will not tunr bt hand, and the drill strains a bit to get it going. I'm going to pull it apart to see what's going on. I have priced new speedos just in case.
Bill Burmeister
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