Here you can get How To Fitting A New Speedometer Cable and Speedometers working.
Speedometer failure is likely to be caused by a fault within the cable that runs from the gearbox to the back of the speedometer gauge. If the gauge needle doesn’t move at all, the inner cable or drive may be broken; or the cable’s square ends may became rounded with wear and fail to engage within the sockets.
The fixings at the ends can work loose or be wrongly fitted. If the gauge needle swings or moves sluggishly, gearbox oil may have seeped up the cable and got into the speedometer itself. therein case, you want to replace the speedometer. If the needle twitches rapidly, see whether the cable is crushed, kinked or too sharply bent. Intermittent twitches are often caused by loose connections or by worn and slipping ends on the cable.
A tapping noise may be a sign of a damaged drive or lack of lubrication. To examine the cable for any of those faults, support the car securely on axle stands or ramps.
Disconnecting and checking the cable
First look over the whole length of the outer cable to see if the casing is broken anywhere. Make sure that the cable follows a smoothly curved route and isn’t kinked or crushed. There should be no bend within 50mm of either end. Bends elsewhere should have a radius of not less than 150mm.
On some cars, guide clips hold the cable in place. make sure that it’s not worked loose. The cable is connected to the gearbox by a knurled thimble nut, a circlip, or a forked plate. Unscrew a thimble nut together with your fingers, starting it with large grips if necessary. Squeeze a circlip free with circlip pliers. A single screw holds a forked retaining plate. Unscrew it. The top end of the cable is harder to reach. If you can’t reach it, remove the speedometer or the instrument panel.
The top connection may be a knurled thimble nut, or one of several types of clip. Most clips release once they are pushed in and turned sideways; one type features a ribbed area on one side, which you depress to release the clip. Examine the square ends of the drive for wear and make sure the fixings are sound. Turn one end of the drive by hand while a helper watches the other end. If the other end doesn’t turn, the drive is broken. If the drive turns stiffly otherwise you feel it snagging, make sure it’s not kinked or crushed by a pointy bend or a guide clip.
If one end of the drive moves during a circle rather than revolving on the spot, the drive is kinked. If the drive seems undamaged but is usually stiff, it’s going to need lubrication. Pull the drive out of the casing, clean the drive with petrol, smear it sparingly with grease and slide it back. Some inner cables, however, have captive ends and you can’t pull them out. therein case, feed light oil between the cable and outer sheath.
Fitting the new cable assembly
Find and release all the guide clips, and lever out the rubber grommet where the cable passes through the bulkhead. Pull the cable out into the engine compartment. Check again that you simply need a new cable. Repeat the turning test to see if the drive is kinked; or pull out the drive and roll it along a flat surface. Hold the cable during a ‘U’ shape about 230mm wide. Turn one end of the drive. It should move smoothly without catching inside the casing.
Sometimes you’ll renew the drive alone, but makers now tend to provide only complete cables. In any case, take the old cable to the parts store to form sure that the new one is identical. it’s a good idea to buy a new gearbox oil seal at the same time. Push the highest end of the new cable through the bulkhead. Use a skinny screwdriver to ease the grommet into place.
Refit the cable into its guide clips. Some clips have bands to mark the points that ought to fit into the clip. they’re a useful make sure you’re routing the cable correctly. In any case, confirm that the route is smoothly curved. Add extra clips or bands as long as they’re really needed. confirm that clips don’t squeeze or pull the cable. To fit the new gearbox oil seal , lever out the old one with a screwdriver and press within the new one, making sure it seats well.
Refit the lower drive connection, taking care that the square drive end is engaged. Tighten a thimble nut only finger tight, and take care to not cross-thread it. The top connection is slightly harder to refit, because it’s more difficult to get the second end of the drive engaged. Refit the speedometer if you had to get rid of it, and test it by taking the car on a brief run.
Cable connections into the gearbox
Speedometer cable connections to the gearbox fall mainly into three types. The knurled thimble-but connection is threaded inside, and screws on to the gearbox speedometer outlet – which is also threaded – up to the shoulder.
The circlip connection fits over the cable and into a recess within the gearbox output sleeve , securing both. The fork connection – an older type – is just a shaped fork that holds the cable end within the gearbox by means of spring pressure. it’s secured by a screw.
- Sleeve connection: A knurled thumble nut screws on to a threaded outlet.
- Circlip connection: A circlip on the cable fits into an outlet.
- Fork connection: The cable end is held by a shaped fork.
How Speedometers work—a closer look
- When the engine turns over, the driveshaft turns to make the wheels spin round.
- The speedometer cable, powered by the driveshaft, turns as well.
- The cable spins a magnet around at the same speed inside the speed cup. The magnet rotates continually in the same direction (in this case, counter-clockwise).
- The spinning magnet creates eddy currents in the speed cup.
- The eddy currents make the speed cup rotate counter-clockwise as well in an attempt to catch up with the magnet. Remember that the magnet and the speed cup are not joined together in any way—there’s air in between them.
- The hair spring tightens, restraining the speed cup so it can turn only a little way.
- As the speed cup turns, it turns the pointer up the dial, indicating the car’s speed.
