Speedometer: Bevel gears hardly turn anymore

B

bikemaniac

Senior Member
Hi,

Last summer I damaged my speedometer cable at the gearbox - it simply twisted the wire inside off. Something must have been stuck so I bought a new speedometer cable. Now, I made some checks and it turns out that my speedometer in the dash is the origin of problems.

It turns out that there is an enourmous drag when turning the drive gear assembly by means of a screw driver. Now it makes total sense that my wire twisted itself apart earlier. I removed the cover plate and had a look at the bevel gears and they seem fine without any damages at all. However when prying the inner bevel gear it is apparant that something needs to be lubed or disassembled.

I removed the entire speedometer from the sheet metal cover and all parts (incl gears) in the front look just fine. However, the bevel gear of my concerns goes into the casting and I cannot disassemble it further.

Does anyone have some ideas on how to make the bevel gear spin smoothly again? I am not looking for a perfect restoration - rather a quick fix.

Lucas
 
You need to remove the whole cover so you can lube all the bushings and gears. Under the small oval cover you can dig out all the old hard grease and squirt some oil on the gears, then spin it with an electric drill. But I wouldn't do this until you remove the main cover and lube every gear and bushing first.

You might get lucky and get things freed up, but the main problem is the old potmetal swells and binds the main shaft with the magnet on top. I put a punch in the center of the magnet hole and gave it a light tap. This freed up my tight shaft, but that shaft is very delicate and if you strike the punch just a little off to the side, you can snap the shaft. I would lube all the parts and see if the drill will get it freed up first, then go from there. If you don't feel comfortable working inside the speedometer, then send it to someone that repairs them.
 
Same problem..... 250 bucks later all reconditioned by professional and good for another 80 years I hope! (Like I would ever know if it lasted that long! )

"A life time guarantee is not what it used to be."
 
I have now disassembled the speedo. Is it true that I cannot disassemble the main shaft with the bevel gear at the bottom and the magnet on the top? My only chance is lubing and tapping with a punch?
Lucas
 
To free up my mainshft, I drilled some 1/16" holes in the housing & injected some 2 cycle oil inside, with a syringe. I FINALLY got it where I could spin it with a stub cable & a drill motor. DON'T spin it very fast!!! To help the oil get into critical places, I laid it in the sun, & turned it over several times.
Bill W.
 
Dig the old hard grease out of the bevel gears, then set the speedometer so you can put some light oil, like automatic ****** fluid, in the bevel gears and let is soak for a day or two. Then try turning the shaft again. I've filed a nail to have a square end, then chuck it in a variable speed drill and spin the shaft. If it starts binding, don't force it, or something will break.
 
I had the same problem with my speedo. After removing the cable from the base of speedo, look inside and you will see a brass nut with 2 holes drilled in it, I used a pair of needle nose pliers to remove the nut. Use a small screw driver to loosen the old grease and blow out with air compressor. Fill this area with a thin solvent like wd40, turn it everyday, it will loosen.
carry on nick c
 
I use the square drive end of a small tap to spin the speedo with a drill.

I think I use a 3/16th whitworth tap , but I guess most small ones are the same size as the end of a speedo cable.
 
I hate to discourage you, but I have been messing with 4 old oval speedometers and 3 of them needed the bevel gears removed to get them working. Do a "Search" in Ford Barn for Gordon Fisher's instructions.
 
I wouldn't used WD-40 on the speedometer because it does bad things to the potmetal frame. For some reason WD-40 and potmetal don't go together well. It could make the bind worse by making it swell more. I've never had a problem by using ATF or a thin oil.
 
Be careful if you try to loosen up the shaft by tapping on the gear end, if the end of the speedometer frame is not properly supported, the magnet shaft will be bent, if you hit it too hard you will end up with to much end play in the magnet shaft, causing the unit to be noisy. Oil the shaft from the gear end, the felt under the magnet and the oil felt.

Mark

Mark's Speedometer
 
Tom Wesenberg said:
I wouldn't used WD-40 on the speedometer because it does bad things to the potmetal frame. For some reason WD-40 and potmetal don't go together well. It could make the bind worse by making it swell more. I've never had a problem by using ATF or a thin oil.
Click to expand...

I used trumpet oil on mine. I bought it at the local music shop
 
So, now I got the main shaft loose. It does not spin freely, but it turns without effort and with little resistance.

Now I am looking at the trip wheels, the ones with the red wheel. The problem is, it turns very easily going backwards making a count down. The red wheel carried the next black wheel easily downwards. But in the normal mode, counting upwards, the red wheel struggles to carry the next black wheel one step up. I really cant find any problems but I have to fiddle a lot with it to make one step up. If I would assemble it right now, put it into the car, something would snap within a few seconds, that is for sure.

One option is to completely remove the trip wheels and drive without them because the odo wheels work perfect.

I do realize that the red wheel is the wheels which has experienced the most wear duringbthe years, but I just cant see any damages or wear marks.

Any suggestions on what to do?

Lucas
 
The 1/10 odometer wheel on the trip odometer does wear more than the rest of them, it is the first to fail. On the left side of the wheel there is a single gear cog that looks like a set of rabbit ears that will engage the wheel next to it once per revolution, rotating it 1/10 of a turn (indexing it to the next number). Since the car is almost always driven in one direction, the wear is on the forward side of this gear, wearing the rabbit ears wider on that side. The best solution is to replace the 1/10 odometer wheel with a new or better one. As far as I know, there are no commercially available ones on the market, I make them custom for my speedometer restorations.

If you pull out the reset stem for the trip odometer, it will disengage the drive to the unit and the main odometer will run fine, while the trip will sit idle.

Mark
 
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