Speedometer drive challenge

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bpaulson
Posts: 8
Joined: Fri Jul 13, 2007 3:17 pm

Speedometer drive challenge

#1

Post by bpaulson » Fri Jan 06, 2006 9:04 pm

Description: What is the best way to find out what is causing the problem

Greetings,

I have a 57 Pan that doesn't seem to like drive units. They seem to set in fine but fail to turn the speedometer. There was a bad unit in the bike when I got it so I just replaced it and found it failed. When I removed the unit I found the same kind of destruction the first one had. What is the best way to find out what is causing the problem? Do I need to take the transmission apart. I hope not as it seems to be working fine other than the speedometer challenge.

Bob



Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Speedometer drive challenge

#2

Post by Cotten » Sat Jan 07, 2006 3:21 am

Bob!

Can you describe the damage to the drive unit?

Are we 1000% certain that we have eliminated all binds and kinks in the cable and housing? Is any of it aftermarket?
Might we have a mismatch of gear ratios (how many teeth inside on the worm and outside on the drive)?

The only internal gearbox woe that I have encountered is when the worm gear on the countershaft cluster is pressed on out-of-true. And that would be easy to correct, but it still means pulling the box apart.

Good luck!

...Cotten

bpaulson
Posts: 8
Joined: Fri Jul 13, 2007 3:17 pm

Re: Speedometer drive challenge

#3

Post by bpaulson » Sat Jan 07, 2006 6:44 am

Thanks for the quick reply.

I think I have it figured out. I emptied the transmission of oil and used a bright light to have a look at the worm gear. it seems to be in good condition. Yes the speedo drive unit is after market and not metal. (In some ways I wish it were metal but as it is some kind of fiber the transmission gear is never at risk.) The challenge seems to be in the cable, it binds and is offer a little to much resistance causing the worm gear to eat the speedo drive gear. I have ordered another cable and will let you know if this a good fix. From what i can figure it doesn't take much to put an end to one of those aftermarket speedo drive gears.

If someone has an original 11 tooth gear and is willing to sell it I would be happy to hear about it.

Thanks again,

Bob

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