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1979 F150 driven gear

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Old Sep 1, 2024 | 11:10 AM
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1979 F150 driven gear
Hi guys, I’ve got a 1979 f150 4.9L custom straight 6, 4 speed manual

I’ve fit a new Speedo as it wasn’t working and it still isn’t. I’ve attached the new Speedo cable onto a drill and it spins the dial so it’s not the cable, I’m assuming it’s the drive gear that’s wrong.

I can’t seem to work out what drive gear it is that I need, would love someone to tell me how many teeth I need. Thanks!
 
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Old Sep 1, 2024 | 01:39 PM
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Someone will ask what your rear end ratio and tire size is.
 
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Old Sep 1, 2024 | 03:30 PM
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How many teeth are on your current gear?
 
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Old Sep 1, 2024 | 10:13 PM
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You haven't given enough information for anyone to know. Go to this site and put in your information to figure it out. Ford Speedometer Calculator
 
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Old Sep 3, 2024 | 09:21 AM
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Originally Posted by scottscott
How many teeth are on your current gear?
I’ll need to take it out, not sure if the previous owner replaced the gear with the wrong one as he replaced the speedo cable
 
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Old Sep 3, 2024 | 09:22 AM
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Originally Posted by 5851a
Someone will ask what your rear end ratio and tire size is.

sorry, I’m completely new to this. How can I find the rear end ratio?
 
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Old Sep 3, 2024 | 12:04 PM
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This is what I’m working with




 
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Old Sep 3, 2024 | 03:32 PM
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It looks like you need to replace the drive gear, the one inside the transmission or transfer case.
 
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Old Sep 3, 2024 | 03:33 PM
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Originally Posted by scottscott
It looks like you need to replace the drive gear, the one inside the transmission or transfer case.
what makes you think that?
 
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Old Sep 3, 2024 | 04:17 PM
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The teeth appear to be worn off of the drive gear. Here's a pic of a random Ford drive gear. Notice how the teeth are the same height across the gear, unlike your current drive gear.

 
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Old Sep 3, 2024 | 04:18 PM
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Originally Posted by scottscott
The teeth appear to be worn off of the drive gear. Here's a pic of a random Ford drive gear. Notice how the teeth are the same height across the gear, unlike your current drive gear.

ahh I see! I appreciate that, seems like I’ve got a much bigger job on my hands now
 
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Old Sep 3, 2024 | 04:27 PM
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Unfortunately, yes, a much bigger job. The driven gear looks OK, but you may want to replace it as well.
 
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Old Sep 3, 2024 | 05:13 PM
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this may be of interest:


 
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