Jumpy speedo needle? Help!

mine did the same, new speedo cable lubed with the included lubricant did the trick...although after 100 miles it now bounces 1-2mph consistantly, and at all speeds(though sometimes at highway speeds it will be steady), also dont buy the cheapest cable you can find, for about 8 bucks more(a different store) the quality difference was worth it(the better cable included the rubber firewall grommet, a tube of special grease, better crimped end pieces, and what looks like a better quality cable)

~Mark~

replacing my cable cured mine - I tried the lube too and it lasted about 3 months.

Speedometer cable replacement for 87-93 Mustangs.

Note: All 89-93 cars have a VSS sensor even if they do not have cruse control. The 87-88 only have a VSS sensor if the have cruse control.
Speedo cable housing assembly without cruse control:


The VSS equipped cars have a speedo cable with a different fitting on the transmission end of the cable. It is the fitting on the LH side of the following picture.

Speedo cable housing assembly with cruse control


1. Inside the car:
1.) Remove the shield around the steering column that covers the ignition switch & turn indicator switch.
2.) You now have access to the two screws that hold the lower part of the cluster housing in place. Remove them and place them in a zip bag.
3.) Use a stubby or an offset Philips screwdriver to remove the two screws on the top of the cluster housing. The screws are up close to the windshield, so they can be hard to get at.
4.) The cluster housing will now slide forward: depending on your particular car, you may or may not have to disconnect the wiring for the headlights, hazard lights, or cluster wiring. All of the wiring uses plastic connectors with plastic spring clips on them. To release the connectors, lift the plastic clips and pull straight back.
5.) The speedo cable is secured in the speedo head by a white plastic clip. Depress the clip or squeeze it and pull the cable out of the speedo head. This can be tricky, but it will come out if you have the white clip depressed enough.

Photo courtesy of ALMOST STOCK

6.) With speedo cable removed from the speedo head, try twisting the cable end with your fingers. If it turns more than 1/4 turn, the cable may either be broken or you have damage at the other end where the cable mates to the VSS sensor or speedo pickup gear in the transmission.
4.
Outside the car, replacing the cable housing assembly. The following steps are necessary only if you plan on replacing the cable & cable housing assembly.
7.) If you are going to the replace the cable housing, the next step is important. Tie a study string or wire to the VSS sensor end of the cable housing. This string or wire is to be used to fish the cable housing back through the maze of wires that is under the dash. If all you are going to do is replace the inner cable, you can omit this step.
8.) Jack up the car, all 4 tires must be off the ground. Place jackstands under the car for safety.
9.) Locate the VSS sensor on the driver’s side of the transmission tailshaft housing. The speedo cable housing will be secured in the VSS sensor with a hairpin clip Do not remove the clip!!!: The hairpin clip stays in place. If you remove it, the odds are that you will not be able to get the cable to stay in place on re-installation. Pull firmly straight back on the cable housing and it will come out. A considerable amount of effort may be required to get the cable out of the VSS sensor, but it will pull out.
10.) Release the cable housing from the clips that secure it to the car body.

Inside the car:
11.) The housing assembly can then be pulled out and the fish string or wire can be removed from the old cable housing and secured to the new one.
12.) The inner cable can be removed by pulling it out of the housing assembly. Watch out for the lubricant so that you don’t get it on the car’s interior.
13.) Lubricate only the lower part of the new cable with speedometer lubricant or graphite. Don’t use too much lubricant, or it will work its way up into the speedo head unit and damage it. Thread the inner cable into the housing, turning it as you go. When you are all the way in with the new cable, it will engage the VSS sensor and stop turning.

Outside the car, replacing the cable housing assembly. The following steps are necessary only if you plan on replacing the cable & cable housing assembly.
14.) Use the fish string or wire to feed the cable housing assembly through the dash wiring and out the cable hole in the firewall.
15.) Secure the cable in the body clips, making sure that the cable isn’t rubbing against the exhaust pipe.
16.) Push the cable housing assembly into the VSS sensor until it snaps in past the hairpin clip.

Inside the car:
17.) Push the cable housing back into the speedo head unit. You should be able to feel the white clip click into place.
18.) Reconnect all the wires & connectors on the speedo head unit.
19.) Re-install the cluster unit in the dash & tighten the 4 screws that hold it in place.
20.) Re-install the cover for the ignition switch & turn signal.
21.) If the car is up on jackstands, start the car, place it in gear & watch the speedo to see if it works OK. If you didn’t jack the car up, take a test drive.

Ugh.....this reminds me I need to replace my cable.

ha. mine does the same thing. Only 65k miles on the damn car

The vss sensor fixed mine on my 87..

if the drive gear in the trans is Yellow (7 tooth) you want to use the red driven gear in the vss. If you put the white gear in there, pull the vss and check it - the white gears have the rp of getting chewed up.

Bottomlesspit said:

I searched today and found a RED gear in my parts bin, so that means there is a WHITE on installed on the car.
Can someone tell me what to expect in terms of speed readouts on my speedomoter between the different gears? Is the RED closer or further than the white from actual?
Reminder: I have 3.73 gearing.

Click to expand...

The 23-tooth (white) gear will be more accurate that the 21-tooth (red), but it will not be correct.

Before 1990, the white speedo driven gear is correct for 3.73 gears (with stock sized tires) because the speedometer drive gear was a 7-tooth gear. After that, the T-5 got an 8-tooth drive gear, and the 23-tooth driven gear was correct for 3.55 rear gears. With 3.73 gears, the white driven gear will get your speedometer reading about 5% too fast. Using the red, 21-tooth gear would add about another 9 or 10% error to your speedometer reading. Tires that are lower profile than stock will further add to the error.

I expect that right now your speedo is indicating 70 mph, when you are actually only going 66 or 67. If you use the red gear, you would only be going about 61 mph while indicating 70.

Assuming your car is a 5-speed, to totally correct the speedometer, you'll have to put in a 6-tooth(black) drive gear paired with an 18 tooth(yellow)driven gear. I have 3:73's and ran the white 23 tooth gear for awile but it started bouncing arround heavily just like you've described.

It more complicated than it's really worth to swap out the drive gear. The gear is located in the tailshaft of the tranny.