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Discussion Starter #1
Ok , so after a lot of help on a different thread about gear ratios where I was not going to be happy with the close ratio top loader I was putting in to replace my 3 speed, I sold the close ratio and purchased a wide ratio with the hurst shifter and linkage, supposed to have been rebuilt and does look like it was , with the exception of the speedo drive gear has some smears on it like someone but the wrong driven gear in and rotated it. It has a black 7 tooth gear in it.
It is an RUG- BJ1 so according to the numbers it would be out of a 72 mustang 351CJ. I need now to get a new speedo cable and will replace the drive gear and get the correct driven gear. So I started looking at speedo cables and one listed for my car ( 71 mach1 ) says ( except 351 4V ) I can't understand what would be different about the cable but anyway if I am putting this message across so it makes sense, Any input on how to find the right cable and figuring out which gears I need would be appreciated. Thanks
 

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Use the correct cable for the year of your car. The hole in the 4-speed trans was the same for all years. The 4-speed cable inserted on the right side, all others on the left side, so the 4-speed cable is much longer. Naturally, the 4-speed cable gear has a left twist, so don't try to use the 3-speed/auto trans gear, which has a right twist.
 

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Discussion Starter #3
don't try to use the 3-speed/auto trans gear, which has a right twist.
I am aware of the directional gears, I think thats what someone did to mar the gear in the trans, So I was looking at a sight a while back explaining how the correct gears are determined ( amount of teeth ) based on your axle ratio etc. And I think there is a range for each. I cannot find that sight now. I was a little confused at wether the different driven gears could work on the same drive gear for different applications, I think from memory I need to replace my black 7 tooth drive gear ( because it has damage) and then figure out which driven gear will work for what will probably end up being a 3.25 rear.
 

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Yes, the driven gears can be driven by all the drive gears, they are not a tight mesh like axle gears.

Try this-
 

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NPD has a speedo cable in the correct length for the 4 speed cars. It's a bit pricey, which I'm going to assume is it's a custom made cable for them.


Everyone else has consolidated the 66" and longer cables into a single 80" unit, which is a PITA to secure under the car.

 

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I used this calculator yesterday to order a replacement drive and driven gear.
Fortunately the black 7 tooth drive gear seems to be the one with the most workable combinations. You can find tire size calculators pretty easily.
 

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Everyone else has consolidated the 66" and longer cables into a single 80" unit, which is a PITA to secure under the car.
True, at least for aftermarket. When the Barn still had a catalog, we would buy the 80" cables by the carton, then cut them down to the Ford specification size, re-crimping the speedometer end, and re-crimping the square drive end on the cable. Fairly simple job, but the darn tool is about $100, if you can find it. Just used it recently to make the cable for this-
760639
 

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Beautiful Daughter,
I recently installed a black 7 tooth drive gear and a 17 tooth driven gear in the top loader for my 73 Mach. I am running 3:25 gear with 255-60-15 rear tires and my speedometer is accurate within a mile an hour, just saying.
Thanks, Jay
 

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Discussion Starter #11
Beautiful Daughter,
I recently installed a black 7 tooth drive gear and a 17 tooth driven gear in the top loader for my 73 Mach. I am running 3:25 gear with 255-60-15 rear tires and my speedometer is accurate within a mile an hour, just saying.
Thanks, Jay
Thanks , Thats what I figured I needed with the use of the web sight supplied. I Already ordered the 17 tooth
 

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Discussion Starter #12 (Edited)
I received the new black 7 tooth drive gear today and it has an extra notch where it fits on the shaft, the one I have removed has a halfway slot for a ball bearing to make it ride with the shaft and only allow it to go in the proper direction. The new one has a slot opposite that that goes all the way through. I am assuming that is for an optional way of holding it on instead of the c clip ?? and that with the c clip I will just install it like the original and just disregard that notch ????, I remember on the close ratio that I sold I could feel a round clip of some kind that this one doesn't have.

Never mind, I finally found the answer, I guess it was an optional way of fastening the gear, Thanks anyway.
 
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