Repairing Jaeger and Smiths Speedometers
An Article by Anthony Rhodes
Anthony (Tony) Rhodes has written a comprehensive article on the various models of the Jaeger and Smiths Speedometers, as used by many British cars, including (with some differences) the Sunbeam Tiger. Tony has graciously consented to allow his article to be reproduced on this web site, and we are grateful.
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This manual covers mechanical Jaeger/Smiths speedometers from the early 1960's through (at least) the late 1970's. I have worked mostly with Triumph parts, but also MG as well. I found that they have essentially the same works inside their different size cases. Therefore, servicing these two types uses similar procedures.
After reading this, PLEASE give me some feedback. I want this manual to be as explicit and accurate as possible. Your comments, both good and critical, will be very useful for my attempts to refine this monograph. If you find that your speedometer differs from my description, please let me know what you found, and the speedometer serial number and the make/year of your car. I want to hear everything! Please email me at ARhodes@compuserve.com.
THE MALFUNCTIONING SPEEDOMETER
You have almost nothing to fear except fear itself. You CAN fix your own speedometer. Here is some information that may help you. The first issue is to decide whether the speedometer itself is actually the cause of the problem. Some faults that are thought to be due to a malfunctioning speedometer are actually due to a problem with the cable running to the speedometer, or with the drive gear in the transmission.
Frequently the cable itself is the cause of a wavering speedometer pointer. It is unfortunately somewhat difficult to service the cable. You must be prepared to get under the car and remove the cable from the transmission. However, it is sometimes possible to service the cable simply from the speedometer end. You need to remove the speedometer, then pull up some slack in the cable so the end of the cable is protruding slightly from the dash. Then you may pull out the wire cable from the outer sheath. Lubricate the cable with white lithium grease or gear oil and then slide the cable back into the sheath. As you get to the last couple of inches you need to slowly spin the cable as you insert it. This will allow the square end of the cable to seat in the square orifice in the transmission drive gear (hopefully). If, after multiple attempts, you can not get the cable to seat, then you will have to get under the car, and unscrew the cable from the transmission. Then press the cable fully in the sheath, and attach the speedometer. Then, back under the car, you must gently seat the cable into the drive on the transmission and screw it down securely. Test the speedometer with the newly lubricated cable. Test this before fully re-installing the speedometer in the dash.
Other causes of a wavering speedometer needle lie inside the speedometer itself. I have seen binding of the input shaft cause wavering as it slows down, then breaks free and turns faster briefly. Binding can also occur between eh shaft and the retaining flange. I have also seen binding in the odometer wheels (particularly the "old" style) cause cyclic resistance against turning, resulting in wavering. There can also be a dirt or lack of lubrication in the needle bushing between the magnet wheel and the pointer spindle. Binding odometer wheels and needle bearings often will casue speedometer wavering that is proportional to road speed.
A speedometer is a simple device. It has three separate functions. The speedometer function is to indicate your speed. There are two odometers which are variations on the same theme. The main odometer shows the cumulative mileage of the car, and the trip odometer measures the mileage since the last reset. The trip odometer is just the same as the main odometer except that it displays 1/10's of miles and is able to be reset. The main odometer has a 1/10 wheel, but it has no lettering and is not shown in the window.