How To Rebuild the Speedometer & Tachometer on a Triumph TR6

I’ve had problems with both the Speedometer and the Tachometer since I bought the car.  The Tachometer was noisy, made a grinding sound.  The Speedometer didn’t work at all. I tried just putting a new cable in the Speedometer.  That worked for about 20 miles, then it snapped too.  The end at the transmission broke. I had been putting it off because I had never taken one apart before.  My speedometer was seized.  When i tried putting an allen head wrench of the approximate size in the back, and turn it, it was frozen up. Follows the procedures below.  And when I was done, my speedometer works, and the tach is quiet!  Not as hard as I thought it would be, with the exception of the odometer.

I found everyone on the forums was referring to:   Anthony Rhodes Speedometer Repair Guide

I found the guide very helpful, printed it out, referred to it as I went.  I did find some “gaps” in the guide that I had to figure out as I went.  Here is what I learned:

Note how accurate your speedo is now – by comparing to a GPS app on your phone for comparison later.

Do NOT bend the spring steel “wings” that are attached to magnet  inside it will throw off the calibration. If someone already has, you can carefully bend them back with goal of getting as much of the flat surface as close as you can w/out touching. By doing this I was able to fix my low reading TACH somewhat.

Be very careful not to damage the inner spring that returns the needle to zero.  If you do you have to send it off to Nisongers or someone else to fix.  It would be really, really easy to wreck the spring if you had your drill motor set the wrong way when “testing” the speedometer.  There is no need to use a drill motor at all, and it would be easy to cause damage.

Mark the disc that moves the needle at zero, so that you can put it back exactly without messing with it unless you need to recalibrate zero.  It is not a disaster if you don’t – you will likely tweak it anyway as explained in that step.

Do you really have to drill the two rivets that hold the inner case together?  Yes, to get to the bushing that you need to clean and lube. You have to do this to clean out the dried grease and lube it, it is not optional.  To replace the rivets I used the largest diameter stainless screws (non magnetic) from Ace hardware that I would w/out drilling/tapping, together with some Loctite to reassemble. I felt they were strong enough, do use the Loctite. No reason to tap the body as others have.

What Grease do you use?  After researching, I used the synthetic grease rated for handgun lubrication, long lasting and rated for heat.  Had some handy.  You could use other synthetic high temp grease.

How do you clean the needle and face?   I was able to clean the needle and face by very lightly dabbing with cotton “Q Tip” like makeup applicators, and 10-1 dilution of Marine Clean (from POR15) with no ill effects on the paint

Should I take the Odometer apart and clean it?  Any tips?  I decided to because of stories about odometers seizing and breaking cables.  Once I got it apart though, it was really clean anyway, not sure I needed to.  The one thing I did do was polish up the brass tube that the cylinders ride on, it was scored.  It was a bit fiddly to get it back together right, and Anthony Rhodes guide isn’t detailed enough.  I figured it out.  But if I had it to do again I would take a video of the disassembly. And I would  put the pieces as I took them off on a coat hanger in proper reassembly order and orientation.
How do you set the mileage on the  odometer?  Before you put the odometer back, hold it carefully so that you have fingers on either side of the brass bushing tube the cylinders ride on.  Hold it loosely.  Take a knife or small screwdriver, and carefully separate the number wheel from the two metal round “gear holders” on either side with all the bits assembled on the brass bushing, but not installed. Adjust, and squeeze back together.

What paint should I use for the outer mounting ring?  SEM  Chassis black Satin is a good paint match

Where can you buy the thick gasket that goes between the glass and the mounting flange (the piece that twists on)?  Buy an extra O Ring, the one that goes between the speedo and dash, and cut about a half inch out of it, and lay it in. Just the right thickness.

The rubber piece that shields one of the idiot lights came loose, how do I reattach it?  I used RTV Silicone.

Where do you buy the thin paper gasket that goes between the glass and the speedo face?  I don’t know, I re-used mine.

How do you calibrate the Speedometer?This is really, really simple if close enough is good enough.  Don’t bother with all the drill motor fuss. Install the Speedometer in the car without the glass, without the lights,  just attach the cable.  Then with a road trip and GPS app on your phone, note how far off you are at your desired speed (like 50mph).  You can only make it accurate at one speed.  Adjust it by removing the Speedometer cable, pull the gauge, remove the two screws, and  adjust the needle (hold the disc, carefully turn the needle).  I am a 3-5 MPH slow at 70. You can mess with the magnets otherwise.

There has got to be an easier way to reinstall the Speedometer/Tachometer in the dash!  When reinstalling, I had a really tough time getting the nut started on the top bracket.  In a moment of inspiration I realized  it is easier to put the top mounting bracket and nut on loosely with the speedo out, and tip it in from the front, and then tighten from the back.  It is pretty easy to get to the bottom bracket and nut on from the back.
Do both the speedo and the tach one right after the other.  It is pretty much the same process, and it is good to do this while it is fresh in your mind.

How do you get the cable ends through the replacement rubber grommets on the firewall?  I couldn’t.  I cut it from the outside to the center, and installed it that way.

What if I want to convert to an Electronic GuageConvert a Gauge

 

 

 

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