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TR2/3/3A Odometer issues???

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K

karls59tr

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The Trip mileage reading at the top appears to be working but the mileage reading at the bottom isn't registering? Are there any known issues a DIY guy could check first to get it working before having to send it out to a shop? Karl
 
Karl. The trip meters each drive via worm gears from a worm on the input shaft of the speedo. The gears are plastic and can and do crack so they do not hold onto their respective shafts, resulting in jamming and teeth shearing from the gear and hence loss of drive to the trip meter. Additionally should the mechanism get fouled with oil and jammed, similar result occurs with sheared teeth on the gear.
Replacement of these gears is a common task for reputable service people and is best attended to by them. DIY involves stripping down the instrument, removing the offending gear, sourcing a replacement and putting the instrument back together.
I have done repairs similar to this on the Smiths chronometric speedos where I have made the gears (brass and phenolic board) and replaced them. More involved than the magnetic speedos of the TRs but I would prefer to outsource the work these days given a choice. Modern replacement gears are (I beleive) produced from a higher quality plastic also.
Should you want to check for interest or peace of mind, disconnect the cable, undo the two retaining nuts and remove the speedo from the dash.
Dismantling the speedo is straight forward. The bezel has tangs on the rear that disengage with the body by turning a few degrees, releasing the bezel and glass.
Don't touch the face as the paimt is easily damaged. Two screws on the rear of the body release the inner mechanism from the body, at which point you will be able to see all the mechanism.
Would love to know the outcome.
Lionel
 
Thanks for the info Lionel. I might try having a look inside the speedo but I will leave it as a winter project as it's still good driving weather here.(y)(y)
 
I'm afraid it will require taking the gage apart to fix. If you are inclined to try it yourself (not for the light hearted, LOL), then I can post some pics of what you are getting into. Most of the units I have taken apart have metal gears, but plastic number wheels. Usually the grease inside gets hard from sitting, which then causes problems. So taking it apart and thoroughly cleaning is enough to get it back working.
 
CJD said:
I'm afraid it will require taking the gage apart to fix. If you are inclined to try it yourself (not for the light hearted, LOL), then I can post some pics of what you are getting into. Most of the units I have taken apart have metal gears, but plastic number wheels. Usually the grease inside gets hard from sitting, which then causes problems. So taking it apart and thoroughly cleaning is enough to get it back working.
Click to expand...
That's good to know that cleaning out the old grease from the gears may solve the problems. I don't want to send it away if I don't have to. I once owned a 76 BMW E12 with the same speedometer issues. Took it apart and the plastic gear had cracked. Turns out it was a very common failure for BMW's of that era. Apparently an upgraded type of plastic gear was required and a BMW club member started manufacturing his own and selling them.
 
Karl,
When you’re ready, I’ve had both speedometers and tachometers repaired and/or restored by MoMa in Albuquerque. Excellent work, good price.
 
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