Finally everything is back together and I took out the Cutlass a couple of weeks back. The speedometer seemed to be working fine, only a little bounce. After about 10 minutes, as I was accelerating, it just stopped around 30mph. It would slowly creep upwards as I maintained probably around 55. Then when I stopped, it remained around 30, with a very slow creep downward. I went home and parked it. The next day, the speedometer read 0, worked fine again for the first 10 minutes or so, then the problem repeated. Any ideas on where to start?

Thanks,
Ken
69 Cutlass S, TH350

 

The speedo head is magnetic drive, so the permanent magnet must be getting weak...needs a speedo repair doc or a fresh speedo

 

Given the slow-to-return-to 0, disassemble and check movement of the needle. Old grease will solidify and act more like glue. SMALL amounts of wd40 can clean the crud out, just be careful not to touch anything else with it. Also the letters and numbers will be very delicate and can smear with just water...
If not comfortable doing this youself, a speedo repair shop will be a good option and they can also check / replace the magnets if they are weak also.

 

Too bad I didn't know of this when I had the dash and gauges out. It worked fine before the disassembly. Just Dashes cleaned the faces, but I didn't have any reason to think I would need an internal clean or repair.

Why couldn't this be as simple as a new cable or gear? Oh well.

Thanks for your help.
Ken

 

Reviving this old thread because I'm having the exact same problem with my just finished frame off on a 72 442 vert. It's a 4 speed and I installed a new cable and tranny drive gear. Was the speedo head the problem? I have a spare head. I had to relocate the output shaft gear aft to get the two gears to line up after I changed the tail shaft housing so the speedo cable woud hook up on the passenger side.

 

If anyone was planning on answering don't bother - tested with another speedo head and did the exact same thing. Must be the speedo drive gear on the tail shaft is somehow mis-aligned with the plastic driven gear.

 

My speedo is not working as of two days ago. I always had a bounce around 60mph, so I will take Robs advice and disassemble the speedo head since I have the dash out.

 

Also you can test them on the bench with a piece of scrap speedo cable and a variable speed drill.

 

Usually this is an indication of a bad cable.

 

I plan to bench test it tonight. Replacing the cable might not be a bad idea. My gear indicating part is broke as well. Does Someone sell just that part

 

Any chance the cable is just dry and needs to be lubed?

 

I will try lubricant too

 

Pull the cable, remove the dried up lube with WD40, then relube with light lithium grease. Made a big difference on mine. If there are any kinks in the cable, replace it.

 

I bench test the speedo tach and seems to be working well.. My gear indicator was broke when I pulled it out so I wonder if you can buy a replacement part for it.. I will start on the cable Monday