Bouncing Speedometer

C

CG McD

Member
Hello all, I have had our P6B 3500S now for 3 months, and getting lots of joy, and lots of tidy ups done after many years in storage. I have a question about the speedo, mine bounces between 0 and 80 kmh at low speed, then gradually settles down a as speed increases, but at 100kmh rhythmically pulsates between 80 and 100. We have removed and replaced and greased the cable assembly to the speedo. Is it worth pulling the speedo out itself? Forgot to mention this is a 1973 car with the round Jaeger Seedo
 
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That does sound more or less like normal behaviour, unfortunately. Greasing the cable will generally reduce the level of fluctuations. Removing the speedo itself won't make a difference unless you have it serviced by an instrument company. My speedo way back in 1987 began fluctuating wildly before it seized, snapping the angle drive on the reverse side in the process. I had it serviced and fitted a new angle drive. It remained steady for many years but now fluctuates plus or minus 2kph at 100kph.

Ron
 
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Be very sparing with grease so that it doesn't get into the speedometer head itself , also ensure the route of the cable has minimum bend radius.
 
I recall my favoured mechanic some years ago having used some special kind of grease intended especially for speedometer cables, but I don't remember what it was called or what it was about it that made it so special! I dimly remember him cautioning me that using any other kind of 'normal' grease wouldn't help, as it would dry and go lumpy and cause more 'sticktion' between the rotating cable and the outer. I also remember him saying their tin of the stuff would last the garage for very many years as it is to be used sparingly, and not for any other job!
 
had same issues ,replaced cable (with outer sheath as a unit) put just 2-3 drops oil in at top end . so far so good as about 2 years no issues but a very small fluctuation still of about 2-3 mph . aware some greases will dry out as suggestion but I would use a low friction wheel bearing grease if I were to remove inner cable and add grease. Grease is after all just a sort of 'soap' with oil mixed in it. I did find after first fitting it had about 5-6 mph fluctuations and did best to route cable with least 'bend(s) ' possible before it settled down.
 
mrtask said:
I recall my favoured mechanic some years ago having used some special kind of grease intended especially for speedometer cables, but I don't remember what it was called or what it was about it that made it so special! I dimly remember him cautioning me that using any other kind of 'normal' grease wouldn't help, as it would dry and go lumpy and cause more 'sticktion' between the rotating cable and the outer. I also remember him saying their tin of the stuff would last the garage for very many years as it is to be used sparingly, and not for any other job!
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I have a feeling it is graphite.

Ron.
 
SydneyRoverP6B said:
I have a feeling it is graphite.

Ron.
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Me too.

I do remember being told many years ago, that you shouldn't grease the end of the cable as it enters the speedo, because if any grease gets into the head, it will make the needle bounce up and down :oops:

Mine does it by BTW;)
 
quattro said:
Me too.

I do remember being told many years ago, that you shouldn't grease the end of the cable as it enters the speedo, because if any grease gets into the head, it will make the needle bounce up and down :oops:

Mine does it by BTW;)
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Thanks so much for the observation and comment. Much appreciated
 
SydneyRoverP6B said:
That does sound more or less like normal behaviour, unfortunately. Greasing the cable will generally reduce the level of fluctuations. Removing the speedo itself won't make a difference unless you have it serviced by an instrument company. My speedo way back in 1987 began fluctuating wildly before it seized, snapping the angle drive on the reverse side in the process. I had it serviced and fitted a new angle drive. It remained steady for many years but now fluctuates plus or minus 2kph at 100kph.

Ron
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Many thanks for this advice and observation, Ron.
 
From your description I suspect the right agle drive behind the speedo needs a drop of oil and a check that the pressed in plate hasn't been hammered out a bit. I only grease the cable with a light oil (like sewing machine oil) with a little graphite grease mixed in for when the oil dries out. Best to remove the whole cable and use a drill to drive the inner core with an in and out motion to spread the lubricant out evenly. you don't need much
 
mikecoombs said:
From your description I suspect the right agle drive behind the speedo needs a drop of oil and a check that the pressed in plate hasn't been hammered out a bit. I only grease the cable with a light oil (like sewing machine oil) with a little graphite grease mixed in for when the oil dries out. Best to remove the whole cable and use a drill to drive the inner core with an in and out motion to spread the lubricant out evenly. you don't need much
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mikecoombs said:
From your description I suspect the right agle drive behind the speedo needs a drop of oil and a check that the pressed in plate hasn't been hammered out a bit. I only grease the cable with a light oil (like sewing machine oil) with a little graphite grease mixed in for when the oil dries out. Best to remove the whole cable and use a drill to drive the inner core with an in and out motion to spread the lubricant out evenly. you don't need much
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Thanks Mike.
I have the dash apart as repaired clock today, I will pull it out further tomorrow to check as you have described. I guess I could drive the speedo with a drill and square attachment temporarily to ensure it is fine.
 
mikecoombs said:
From your description I suspect the right agle drive behind the speedo needs a drop of oil and a check that the pressed in plate hasn't been hammered out a bit. I only grease the cable with a light oil (like sewing machine oil) with a little graphite grease mixed in for when the oil dries out. Best to remove the whole cable and use a drill to drive the inner core with an in and out motion to spread the lubricant out evenly. you don't need much
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Extracted the Speedo today, and took off the angle drive, it was very stiff to operate. A large matchstick in a battery drill directly proved the speedo itself to be fine and steady. Lubed the angle drive and used the matchstick and drill to exercise and distribute lubrication. Re attached to speedo, and tested, nice and smooth. Once all back in the car, it sure had cured the low speed megabouncing, and only still have 15kmh rhythmic bounce at higher speeds, 100kmh. I will look to disconnnect the other end of the cable and check the routeing, if not that then, I guess its an abberation/problem at the primary speed source.
 
juts a note but WD40 oil does not dry out as does normal oils ( leaving stickiness ) . might be worth checking out lube for mechanical clocks as that uses non drying ( sticky) oils.
 
Check the cable routeing for kinks, then make sure that the gearbox rear flange retaining nut is tight.
 
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