Speedo cable breaking.

[Keith Clements]

Try checking there is no binding inside speedo by rotating cable by hand at the gearbox end . A few hundred turns may be necessary to check that trip is not binding

[aj4cks]

New inner and outer Speedo cable, worked fine for 7 miles before braking at gearbox end so cannot think it was a binding issue

[aj4cks]

Turning by hand a few hundred times would keep you busy for a long time. Am I misunderstanding

[Keith Clements]

The trip drive is separate from the speedo and thus it could be jamming when the trip goes over 10 miles or 100 or 1000.

You can drive the speedo with a drill set to low speed and low torque ( or drive via a plastic tube to limit torque).

Also check that there is no debris in the gearbox gear socket which would bind the cable. When screwing up there should not be any force required . The outer cable should be just free to move.

The speedo end of the cable also needs to be checked. If too much force is used to tighten , this can cause the bearing surface to bind ...perhaps there was sufficient lubrication for 7 miles then it seized up.

When you fit the next cable, check free movement of the cable, first when fitting to one end, then take off and then check the other end.
It is possible the cable has ends that are too long. Having played with such cables many times fitting Haldas and Speedpilots for rallying one learns to check these things. Sometimes wear on the speedo makes getting the correct fitting difficult.

[aj4cks]

Thanks Keith, I purchased the cable from Catmint who now run JOAC spares. The ends were a real struggle to get the threads to bite unlike the old brass ones. Could not screw on easily by hand and I did use molegrips to nip up. The driver square at both ends were shorter than the original

[Keith Clements]

It may be that the thread on the fitting was wrong. I have had a similar experience. It does go on but is cutting a new thread! I now check on a spare output gear before fitting.

[aj4cks]

Have emailed the supplier and awaiting response

[Keith Clements]

http://www.gaggs.co.uk/html/cable.html

WArning from them!

Also. http://obswww.unige.ch/~wildif/cars/doc ... repair.pdf

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.

There is one school of thought which says the speedo cable should not be lubricated with grease and only use dry graphite.

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 the 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 cause speedometer wavering that is proportional to road speed.

[Chris Spencer]

I have just put a new speedo cable on the Javelin - supplied by Jowett Car Spares - all good and a prefect fit

[aj4cks]

Fitted a second new Speedo cable but this time only finger tight. Drove around the block up to 25 mph, Speedo worked fine.
In the garage I checked the cable was not looping and all ok.
Today reversing out the garage I heard some odd clunking noise, drove forward and then parked up. The cable had looped and the inner cable had snapped again, this time at the entry into the gearbox. Is the problem more likely to be the Speedo jamming than a problem with the gearbox drive? If it’s the gearbox drive is it a case of removing it along with the engine ? Not looking forward to it if it is.

[Keith Clements]

When you fit the next cable, check free movement of the cable, first when fitting to one end, then take off and then check the other end

Posted on June 3rd ...my birthday.
As per telcon tonight...I think the problem is a locked gearbox in the speedo as per picture. This can be caused by wear and tightening the cable boss up too tight.

[aj4cks]

Speedo back in and working, also the clock. Repaired by Speedycables

[Chris Spencer]

Should the speedo require parts or a rebuild - Jowett Car Spares have a specialist supplier that can undertake the work for you

[aj4cks]

Speedycables repaired the speedo and electric clock