Speedo cable...
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Junior User
Joined: Nov 2003
Posts: 64
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From: Hendersonville TN
Speedo cable...
I need to have one made...I'm running a different transmission(Saginaw 4spd)and different size tires than stock...I want to use the stock speedo...is there some kind of formula I need to use to figure this,or who can I call?Thanks!
Posting Guru
Joined: Mar 2003
Posts: 1,734
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From: Kansas City area
Coley -
I'm not sure I completely understand your question....are you wanting to modify the existing speedo to compensate for the tire size, rear end ratio, and trans you are running?? Any good speedometer repair shop can do this for you but you need to collect some data first. Take your truck on a highway that has mile markers. Go ten miles and note what your odometer reads, either more or less or exactly ten miles. This will give the speedometer shop the info they need to correct your speedometer to read accurately. Of course, if it reads 10 miles after you've gone 10 miles according to the mile markers you don't need any correction. Hope this helps.
Larry
I'm not sure I completely understand your question....are you wanting to modify the existing speedo to compensate for the tire size, rear end ratio, and trans you are running?? Any good speedometer repair shop can do this for you but you need to collect some data first. Take your truck on a highway that has mile markers. Go ten miles and note what your odometer reads, either more or less or exactly ten miles. This will give the speedometer shop the info they need to correct your speedometer to read accurately. Of course, if it reads 10 miles after you've gone 10 miles according to the mile markers you don't need any correction. Hope this helps.
Larry
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Junior User
Joined: Nov 2003
Posts: 64
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From: Hendersonville TN
The numbers on my odometer are obliterated...and when I bought my truck there was no cable at all.Do I have to know the transmission ratios too?I have the tire size and rear end ratios...My wife wants to drive the truck some and insists that the speedo work...where could I find the transmission ratios at?thanks!
Lead Driver
Joined: Apr 2002
Posts: 8,813
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From: Littleton, New Hampshire
The cheap way to do this...
Go to NAPA and get a universal speedometer cable and housing. There are a couple of kinds, so get the one with the right fittings on each end and be sure it's long enough. If you can't find a universal one, try one for a 55-57 Chevy and I think that might have the correct fittings. If you have a speedometer gear in the tranny now, hook it up and drive it to see how far you are off. If the speedometer reads too high, you need a speedometer gear with MORE teeth. If it reads low, you need one with LESS teeth. Each tooth is worth about 5 MPH. It is possible to have a combination of tires and rear end ratio for which there is no speedometer gear. In that case, you will have to have the speedometer recalibrated by a shop, but you should be able to get close...
Go to NAPA and get a universal speedometer cable and housing. There are a couple of kinds, so get the one with the right fittings on each end and be sure it's long enough. If you can't find a universal one, try one for a 55-57 Chevy and I think that might have the correct fittings. If you have a speedometer gear in the tranny now, hook it up and drive it to see how far you are off. If the speedometer reads too high, you need a speedometer gear with MORE teeth. If it reads low, you need one with LESS teeth. Each tooth is worth about 5 MPH. It is possible to have a combination of tires and rear end ratio for which there is no speedometer gear. In that case, you will have to have the speedometer recalibrated by a shop, but you should be able to get close...
Senior User
Joined: Oct 2003
Posts: 111
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From: Illinois
Go to www.sccoa.com/faq/speedgr.htm mess with the speedometer calculator there. Maybe it will help, maybe not.
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