Anyone have any experience with Speedometers?

Terry NJ

Terry NJ

Well-known member
The next problem with the coupe, The speedometer! It was working, then one day after a fast run, I noticed it was still. No speed or mileage.Tonight I crept underneath and took the drive gear off. It is the keyed shaft type. I fitted the cable drive and spun it and it was free. All was OK down below. Topside, I have checked the square drive in the back of the gauge. Everything seems OK. Does this sound like a busted meter? I have a spare, but the numbers need replacing so I haven't swapped them yet. Plus I've been fiddlin' with the running gear and the engine so I haven't devoted much time or effort to the speedometer. I've oiled the bearings that I can get at without disassembly.
Terry
 
same with Papa, there are 2 different sized square drives in the speedometer BTW, the cable could have twisted apart in the housing too. I have seen a fair share of stripped speedometer drive gears off the driveshaft as well...
 
A minor extra test before you act: One of the little square bits that come in sets approximates speedo drive well enough to work. Give your speedometer a spin with such a bit and an electric screwdriver or drill. That will definitively pin down the problem as speedo or something in drive. And you can very roughly gauge what speedometer reads if you know RPM of the tool, comparing that to the 1000 RPM=60 MPH of the gauge.
 
Bruce Lancaster said:
A minor extra test before you act: One of the little square bits that come in sets approximates speedo drive well enough to work. Give your speedometer a spin with such a bit and an electric screwdriver or drill. That will definitively pin down the problem as speedo or something in drive. And you can very roughly gauge what speedometer reads if you know RPM of the tool, comparing that to the 1000 RPM=60 MPH of the gauge.
Click to expand...

Now that is a great idea!
 
The way I read your original post it is clear that you ensured the speedometer cable is not binding, but did you check to see if it is broken?

Forgive me if I read your post wrong.

Ken
 
First make sure your main shaft is not binding. A common problem. You should be able to turn the speedo shaft with your fingers.
 
Make sure that the square drive end on the cable is the correct one for your speedometer, ovals used .124 square, round faced units used .104 square. I am posting a copy of my speedometer notes that I send out to my customers with some info regarding the care and feeding of these instruments.
Mark’s Model A Service, Llc

33691 Finley Point Rd.

Polson, MT 59860

Marksspeedometer.com​
Notes on your rebuilt speedometer​
This instrument has been completely rebuilt. It has been disassembled, cleaned, inspected, lubricated, carefully reassembled, and calibrated. Every care has been taken to create a speedometer that looks and performs as well as when it was new. There are some things to keep in mind.
1) Make sure that the end of your speedometer cable is in good condition. If it is rounded on the corners where it goes into the speedometer head, it may slip instead of turning the speedometer.
2) If the instrument is an Oval (28-mid 30), make sure that the end of the cable is .120-.124 square. Make sure that the cable will insert into the speedometer head far enough. The depth of the hole is about 7/16”, but the first 1/8” is round, then it transitions to a square hole. The end of the cable must extend far enough into the head so that it goes at least 3/8” into the input end. The later round units and most other cables are .104 square. They will work for a little while, but will start slipping and round out the drive in the bottom of the speedometer.
3) Now is a good time to inspect and relube the speedometer cable, looking for kinks and places where it is starting to fray. These will catch on the inside of the housing and make the speedometer reading erratic.
4) Make sure that the cable starts squarely into the bottom of the unit; they are easily cross-threaded.
5) There are other factors that affect accuracy other than the speedometer unit. Tire size, rear axle ratio, and drive gear tooth count at the torque tube all make a difference on how the unit will read. I calibrate the units to the standard, which is 1000 revs/mile. If your speedometer is not reading correctly, check the odometer against the mile posts along the highway for several miles, if the odometer is not reading the same as the mileage posts then the cable is not turning 1000 rev/mile. (Most likely the speedometer error will be the same percentage amount in the same direction.)
Any question, contact me @ 406-249-3104
Thanks,
Mark Nelson


 
Hay you can send it to any of us and we will do a good job. One rebuild dose not try to out build a other. But if you do not get it working I will be very happy to make any repairs that are needed. jrnichols642@yahoo.com I have been doing them for over 20 years.
 
I'm a repeat customer with Papanick. I couldn't be more satisfied. Jr. does it right! I'm sure others would also, but my experience has been with him. Ed in Mississippi
 
You must log in or register to reply here.
Back
Top