Speedometer needle erratic.

[Jughead]

My speedometer needles bounces under acceleration and is just about useless. Reads that I'm going 60-80 when I'm about 40-50 and bounces up and down. where should I start looking?
I couldn't get the search function to work.

Thanks
Len

 

[Carney Woods]

Change the speedo cable, almost all mustangs have this problem...............

 

[cjman15]

did you have gears installed? it sounds you might need a new speedo gear... a bouncing speedo is a sign of a broken speedo gear anyway, mine does tha same thing... i've never got around to fixing it tho

 

[Jughead]

Ok, thanks. When I went to track down the cable, it's asking w/speed sensor and w/o speed sensor??? How do I tell which one I need? where's the speed sensor?

 

[TheBocSez]

Mine was doing the same thing. I replaced the speedo gear in the transmission, still bounced. Changed the speedo cable, still bounced. Finally just bought a used speedo in good condtion and now NO BOUNCE!! There are gears and bearing in the speedo itself that I assume also wear out with time. You may end up with the same problem. If you by chance have an 85 mph speedo and want another one to try let me know, I have a nice one laying around that Ill sell cheap but you probably have the 140.

Ok, thanks. When I went to track down the cable, it's asking w/speed sensor and w/o speed sensor??? How do I tell which one I need? where's the speed sensor?

Follow the cable into the transmission. The cable runs into sensor, the sensor bolts into the side of the tranny and the speedo gear is clipped to the sensor. This is on an AOD but I imagine a 5spd is the same. Looks like this
http://secure.50resto.com/product1.cfm?SID=1&Product_ID=2280&Category_ID=145

 

[Jughead]

Ok, I got the new cable and have the gauge cluster out. The manual says to pull the old cable out from the tranny end. Is the cable inside a tube (manual calls it a sheath) which will remain?

 

[TheBocSez]

When I bought a new cable, it was the entire assembly, its a plastic tube with a squared metal "wire" inside. That is the actual cable with the protective plastic outer. Did you get the whole thing or just the metal cable? If the cable only, you will have to disconnect the assembly, pull the cable out and thread the new cable in. If you have a whole new assemly, disconnect the assemly from the tranny and dash, and there is 1 or 2 brackets on the frame that secure it, then pull the whole thing and reroute the new one.

 

[Jughead]

I got a cab;e much like you described. Is the cable hole close to the gauge cluster? My fear is that I'll pull the old cable out and not be able to find the hole in the firewall.

 

[gopher_6_9]

I got a cab;e much like you described. Is the cable hole close to the gauge cluster? My fear is that I'll pull the old cable out and not be able to find the hole in the firewall.

We always tie the new one to the old one and pull it through.

 

[Jughead]

View attachment 523843

 

[795.0pacecar]

My speedo would do the same thing as yours so I bought a 140 mph one, it still bounced but it was alot more accurate, so I got a new cable but I messed up the speedo gear alittle so it bounces till about 25mph then its smooth. If I were you I would get the whole cable, plastic sheath and all because normally it isnt the cable itself that goes bad its the sheath.