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I am getting close to a final engineering inspection on the wagon. Got the seats and belts in, corrected some more fiddly crap, and took it to get the exhaust quietened down. Found that the 205 tyres rub on the front guards, so swapped to 195s on the front.

The speedo had seized during storage (it is an original EK one that I pulled apart and painted the face on - thanks Matty Martin). I freed it up (slight force on the speedo with a length of busted speedo cable, and a very small dab of WD40). Figured that I could then check it whilst trundling round for the tyre and exhaust work. It was pretty evident that the speedo was out. We checked the speedo against one of the speedo apps, with Number 1 Son taking notes while I drive.

The initial run suggested we had a simple % error - the speedo read about 35% too fast whilst driving. This is the original EK speedo head, EK cable, and a TH350 box. Nice gentle bends in the speedo cable. Speedo is a little bouncy, but not much worse than the FB or Grace's ute.

I checked the gear colours in the TH350 (8-tooth orange drive gear, 22-tooth grey driven gear). My maths says that the speedo needs to slow down, so the driven gear needs more teeth. The grey driven gear has about as many teeth as you can get - the only other option is to change both drive and driven gears. I learnt an important lesson - TH350 speedo gears come in a "big" drive gear type, and a "small" drive gear type. Each type needs their own driven gear (ie you cant run a "big" series drive gear with a "small" series driven gear).

I called up the gearbox shop to order some new gears to slow the speedo down. I thought this would be as simple as "please give me a ratio that runs the cable 35% slower". Alas, the gearbox shop wanted diff ratio and tyre size so they could calculate the gears. Their maths said that I needed a smaller driven gear... this did not feel right to me, or the gearbox shop. They thought that perhaps my speedo was crook. The speedo occasionally sticks at 20mph with the car stationary. Perhaps it is crook inside. Back to square one, and some more road testing.

Some more data points with Number 1 son are shown below.
I recognise the readings are only to 60km/h, but need to limit the testing to something sensible - NSW law lets you drive unregistered to test (or repair) after an inspection, but I'm figuring a 100km/h run up the M4 might be pushing the limits. There is some noise in the readings, though they seem to say that the speedo error is not a simple % - the speedo is out a lot at low speed, and gets better at higher speed. A simple ratio change will not fix this.

I'm figuring the speedo head is crook, possibly dirty/corroded/gummed up internally (if anyone has a better explanation of the results above, please let me know). I could swap it for another one (I have one spare), but by the time I get it out and swap the fancy face over I may as well get it repaired.

Anyone know a reputable business who can rebuild a speedo head? Prefer Sydney, but can post if needs be.

Cheers,
Harv

Hi Harv, can’t help with a speedo rebuilder but to fault find further and determine which end is the problem, have you tried some crude bench testing?
You said you had some broken speedo cable and I seem to remember you have a lathe? If not, a bench or hand drill will do - it’s just handy to know how many rev’s you’re doing for consistency.
If it’s not too hard, pull your other spare head unit out, stick the broken cable into it, with the other end in a spinny thing and record the readings at different rpm, then do the same with the other speedo. It might give you a better idea of where the problem is ie. gearbox end or head unit end. This assumes your spare works correctly which, if you’re not sure, you could take it on a road test like you did with your current one

Also, there isn’t much in a speedo, basically a spinning magnet, a not so spinning cup, a hair spring , shaft and pointer. You could look inside for anything obvious and, if you’re lucky, it might just need some corrosion or muck cleaned out
Cheers and good luck with it,

John

Harv,

I would suggest D.I.Y. Automotive Instrument Repairs and Calibrations of Greystanes.

Your speedo shaft seized up from lack of lubrication: there's a felt wick oiler half-covered by the speedo case. Remove speedo from car, remove glass and bezel. Undo the two screws at the back of the case, and lift the mechanism out complete. Remove the rubber gasket if it comes out with the mechanism. The oiler is in a cross-drilled hole with a small Welch plug holding it in. Use an O-ring removing tool to get the plug out, then a pair of tweezers to fish the felt out. Wash the felt out in turps or kero.

Get your piece of busted cable, insert it in the drive end and rotate with your fingers. The drive "should" feel smooth and slightly viscous by hand. If it has any tendency towards binding or stiffness or feels like it "catches" once per revolution, you will need to get some solvent in to dissolve the gunk, and then re-lubricate with sewing machine oil. WD-40 works well as the solvent, but it may take a day or two to free up gummy lubricant. Patience, Grasshopper. Only when the speedo drive shaft feels completely free by hand should you oil the shaft. Then put a couple of drops of sewing machine oil on the felt, put it back in its hole, and follow with the Welch plug.

(I did this after my FC's speedo seized up solid just out of Leonora . . . )

Check the operation of the speedo head with the length of cable and a drill. If the drive is free and well-lubed, the arc (was going to say needle) should not waver, even at low speed.

It's a good idea also to check that the arc runs freely on its pivots, without binding or looseness.

Inside the speedo is a "zero-adjust" which the hairspring anchors to. It looks like a metal arm projecting out from the Nikola-Tesla-rotating-magnet-eddy-current-cup-thing. It's used to set the pre-load of the hairspring when the pointer returns to the zero-stop. If you move the arm, you can vary the speedo error - but it's a uniform error, independent of road speed. So, for example, you may have to get going at 15 mph (say) before the pointer moves off the zero stop. At 30 mph indicated, the road speed is 45; at 60 indicated, you're doing 75, and so on.

The outer end of the hairspring is retained by a taper pin. If you change how many turns of the hairspring are active, you can correct for scale errors in the speedo (think y = mx + b. The zero-adjust above changes b, varying the number of active turns of the hairspring changes m). This will change how the speedometer relates to the odometer, though. I have a suspicion that most speedometers are set up so that 1000 input rpm should give 60 mph on the speedo, one mile per minute on the odometer. Let me see. 60 mph, 3000 engine rpm, times 8, divided by 23 = 1030.

Executive Summary: Lubricate the speedo well and check that the internals are in good order. Do an A-B test in the FB or Grace's ute with smartphone GPS to check the calibration of both (or all three). Then work out what drive gear ratios you'll need in the transmission.

I don't think you'll need to get the speedo rebuilt.

Rob

Great, detailed post Rob

Cheers,

John

Sounds like you have it covered Harv but if not let me know - the guy that tidied mine up also rebuilds but he's in Melbourne - Nunawading.

Thankyou gentlemen... very much appreciated.

If you hear any loud noises, it's only me swearing at the speedo guts.

Cheers,
Harv

Just to add to Robs very comprehensive instructions, and this is relatively obvious so you probably already have it covered, be sure you cable is well lubricated, at least the bottom two thirds. Dry cable can cause the speedo to fluctuate but too much oil or grease at the top will get in to the speedo head and make a mess.

Have fun playing with those delicate bits. Simple maths tells you the drive gear sets will allow you to adjust displayed speed by about 5% which is as good as most OEM units get. Playing with the scale error adjustment in the speedo itself is about the only option when you do a diff change with crash box. Excepting using FX FJ drive gear of course.


Sent from my iPhone using Tapatalk

What about a cosmetic resto ? Has anyone repainted the green numbers on the clear bit of the speedo ? I have one that needs a clean up ? Maybe need the metal bits repainted/reprinted too ???

I had mine done recently Blacky - came up mint.

Was arranged by the panel beater but I can get a contact if you like.

Blacky wrote: Tue Feb 12, 2019 9:58 pm What about a cosmetic resto ? Has anyone repainted the green numbers on the clear bit of the speedo ? I have one that needs a clean up ? Maybe need the metal bits repainted/reprinted too ???

Matty Martin did a really good post on how to do the cosmetic resto here:
http://www.fbekholden.com/forum/viewtop ... edo#p20261

I used it on the wagon gauges, painted the faces a flat white and did the plastic numbers in red.
Not sure what you would use to replicate the original "green" colour on the letters though. Knowing my luck it is some 1950's radioactive stuff like old watch dial paint that glows in the dark. Make me turn into Godzilla.

Cheers,
Harv

ardiesse wrote: Mon Feb 11, 2019 5:56 pm I would suggest D.I.Y. Automotive Instrument Repairs and Calibrations of Greystanes.

I changed the signage from D.I.Y Kids Cars Repairs of Greystanes to D.I.Y. Automotive Instrument Repairs and Calibrations of Greystanes. All good to go.

ardiesse wrote: Mon Feb 11, 2019 5:56 pm Remove speedo from car, remove glass and bezel.

Take whole dash assembly out, two Phillips head screws let the speedo fall out. Prise up some of the chrome tabs around the edge of the speedo...
... and the glass and bezel falls out. Put it onto the nice clean paper that you laid on the bench to avoid marking any of the gauge face.

ardiesse wrote: Mon Feb 11, 2019 5:56 pmUndo the two screws at the back of the case,

ardiesse wrote: Mon Feb 11, 2019 5:56 pm and lift the mechanism out complete. Remove the rubber gasket if it comes out with the mechanism.

ardiesse wrote: Mon Feb 11, 2019 5:56 pm The oiler is in a cross-drilled hole with a small Welch plug holding it in. Use an O-ring removing tool to get the plug out,

ardiesse wrote: Mon Feb 11, 2019 5:56 pmthen a pair of tweezers to fish the felt out.

ardiesse wrote: Mon Feb 11, 2019 5:56 pmWash the felt out in turps or kero.

If you use a small medicine cup, the kids will later wonder why the medicine tastes like kero and NASCO grease residue

ardiesse wrote: Mon Feb 11, 2019 5:56 pmGet your piece of busted cable, insert it in the drive end and rotate with your fingers.

When reclaiming a busted speedo cable, keep both ends. Cut one 6" long to use with your fingers (this is handy to use with the speed in the car), and cut the other end short to go in a drill. 6" of speedo cable in a drill will tend to bow and whip around.

ardiesse wrote: Mon Feb 11, 2019 5:56 pmThe drive "should" feel smooth and slightly viscous by hand.

Speedo feels smooth, but does not always want to go back to zero. It is sticky in there somewhere. Cheers,
Harv

ardiesse wrote: Mon Feb 11, 2019 5:56 pmyou will need to get some solvent in to dissolve the gunk, and then re-lubricate with sewing machine oil. WD-40 works well as the solvent, but it may take a day or two to free up gummy lubricant.

Solvent going in...

... and some gunk starting to come out:

ardiesse wrote: Mon Feb 11, 2019 5:56 pmPatience, Grasshopper. Only when the speedo drive shaft feels completely free by hand should you oil the shaft.

Yes Master Po. I now see the great clarity that instructs your efforts.

Sadly back to work again, so the WD40 has a lot of time to work

ardiesse wrote: Mon Feb 11, 2019 5:56 pmInside the speedo is a "zero-adjust" which the hairspring anchors to. It looks like a metal arm projecting out from the Nikola-Tesla-rotating-magnet-eddy-current-cup-thing. It's used to set the pre-load of the hairspring when the pointer returns to the zero-stop. If you move the arm, you can vary the speedo error - but it's a uniform error, independent of road speed. So, for example, you may have to get going at 15 mph (say) before the pointer moves off the zero stop. At 30 mph indicated, the road speed is 45; at 60 indicated, you're doing 75, and so on.

The outer end of the hairspring is retained by a taper pin. If you change how many turns of the hairspring are active, you can correct for scale errors in the speedo (think y = mx + b. The zero-adjust above changes b, varying the number of active turns of the hairspring changes m). This will change how the speedometer relates to the odometer, though. I have a suspicion that most speedometers are set up so that 1000 input rpm should give 60 mph on the speedo, one mile per minute on the odometer. Let me see. 60 mph, 3000 engine rpm, times 8, divided by 23 = 1030.

I'm guessing it is this doglegged arm, and that to adjust the taper pin you rotate the arm?
There doesn't seem to be much holding it in place... perhaps lift slightly and turn?

Cheers,
Harv

Ringwood Speedometers was the guys - they had the green paint which is a fluorescent of some kind

Blacky wrote: Tue Feb 12, 2019 9:58 pm What about a cosmetic resto ? Has anyone repainted the green numbers on the clear bit of the speedo ? I have one that needs a clean up ? Maybe need the metal bits repainted/reprinted too ???

FJWALLY wrote: Wed Feb 13, 2019 7:56 am Ringwood Speedometers was the guys - they had the green paint which is a fluorescent of some kind

Blacky wrote: Tue Feb 12, 2019 9:58 pm What about a cosmetic resto ? Has anyone repainted the green numbers on the clear bit of the speedo ? I have one that needs a clean up ? Maybe need the metal bits repainted/reprinted too ???

Thanks mate , will call them today

Hi Harv when I did my FC Sedan I didn't change the gear in the TH700 but did some runs with the GPS Speedo on the phone and noted down the difference; from memory I did them at 60, 80, 90, 100 & 120 and then went to some guys over here (trying to remember company name ) they made me up a coverter box that screws in between the gearbox outlet and the speedo cable and brings the speedo into cal.

Let me know if you are interested and I will dig out the company details.
Neil