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Old 03-02-2026, 02:32 PM   #1
r8rs4lf
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Leakage through speedometer cable

Is there some type of seal or o ring that I can buy to seal the speedometer cable to the transmission or is a new cable needed? I tried to tighten it up to no avail.

I think I found a small leak.

No idea why photos are turned sideways.
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Old 03-02-2026, 03:18 PM   #2
68Gold/white
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Re: Leakage through speedometer cable

There's 2 seals there.
Remove the bolt and metal piece, pull on the cable, and the entire piece will come out of trans with the pencil gear. There's an "O" ring on that housing, replace that.

Unscrew the cable from the small housing piece, there's a rubber seal inside that. It seals the pencil gear.

There's 2 different types oseal for the pencil gear. The most common one, I thought is just rubber, make sure the lip points inward.

A month ago on my buddies 71 C10. I discovered the small seal in his was a steel shell with inner rubber, just like a front bearing seal but smaller. I'VE NEVER SEEN ONE OF THESE, EVER!!! But OReillys sells these. it'a a bear to get out of that housing.
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Old 03-02-2026, 04:19 PM   #3
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Re: Leakage through speedometer cable

Quote:
Originally Posted by r8rs4lf View Post
Is there some type of seal or o ring that I can buy to seal the speedometer cable to the transmission or is a new cable needed? I tried to tighten it up to no avail.

I think I found a small leak.

No idea why photos are turned sideways.
You can buy the whole "bullet" that has the o rings on it or try to find o rings. I prefer the new bullet. Cheap and easy. Unscrew speedo cable and take nut and keeper out. There's a good chance the driven gear is worn and it won't seal against the o ring inside the bullet. Check the color and number of teeth. Cheap and you should replace it while it's apart or you might not fix your leak the first try. The gears and bullet are cheap. Vendors should have them. I bought mine on Amazon ..
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Old 03-02-2026, 04:43 PM   #4
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Re: Leakage through speedometer cable

<sips -r 90 IMG_210*.jpg>
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Old 03-02-2026, 04:57 PM   #5
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Re: Leakage through speedometer cable

bullet looks like this
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Old 03-02-2026, 06:46 PM   #6
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Re: Leakage through speedometer cable

Be aware!
Some of those new ‘bullets’ don’t come with the internal o-ring.
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Old 03-03-2026, 10:27 AM   #7
72c20customcamper
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Re: Leakage through speedometer cable

I bought this tool to remove and replace the shift shaft seal on my truck . Worked very well .
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Old 03-03-2026, 11:09 AM   #8
r8rs4lf
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Re: Leakage through speedometer cable

Quote:
Originally Posted by howzzzit View Post
You can buy the whole "bullet" that has the o rings on it or try to find o rings. I prefer the new bullet. Cheap and easy. Unscrew speedo cable and take nut and keeper out. There's a good chance the driven gear is worn and it won't seal against the o ring inside the bullet. Check the color and number of teeth. Cheap and you should replace it while it's apart or you might not fix your leak the first try. The gears and bullet are cheap. Vendors should have them. I bought mine on Amazon ..
I went to my local auto parts, didn't have it so I ordered the whole kit from Amazon. Never did I think I would be ordering truck parts from Amazon.

This is the kit I ordered.

I'm not sure which gear I have, but my speedometer is off anyways so I'll be able to fix that as well.
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Old 03-03-2026, 01:11 PM   #9
Rust_never_sleeps
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Re: Leakage through speedometer cable

I bought the same-ish kit from Speedway, but I'm not sure it includes the inside seal
It did include a set of matching ring gears, fwiw
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Old 03-03-2026, 01:33 PM   #10
howzzzit
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Re: Leakage through speedometer cable

Quote:
Originally Posted by r8rs4lf View Post
I went to my local auto parts, didn't have it so I ordered the whole kit from Amazon. Never did I think I would be ordering truck parts from Amazon.

This is the kit I ordered.

I'm not sure which gear I have, but my speedometer is off anyways so I'll be able to fix that as well.
When you change the gear you can load handy speedometer apps on your phone. They hook up to several satellites and will give you a pretty accurate indication of your speed. While you have the bullet removed check the color of the gear inside your transmission. You can then choose the correct driven gear if yours is incorrect. Can't remember where, but there are sites that can help with choosing the correct gear. You can see it with a flashlight. It's a pretty easy fix and you'll be happy without a drip drip.
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Old 03-03-2026, 02:36 PM   #11
r8rs4lf
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Re: Leakage through speedometer cable

Quote:
Originally Posted by Rust_never_sleeps View Post
I bought the same-ish kit from Speedway, but I'm not sure it includes the inside seal
It did include a set of matching ring gears, fwiw
So there's another seal inside the bullet?

Besides the one that goes on the end where the gear is pushed in?
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Old 03-03-2026, 02:49 PM   #12
r8rs4lf
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Re: Leakage through speedometer cable

Quote:
Originally Posted by howzzzit View Post
While you have the bullet removed check the color of the gear inside your transmission. You can then choose the correct driven gear if yours is incorrect. Can't remember where, but there are sites that can help with choosing the correct gear. You can see it with a flashlight. It's a pretty easy fix and you'll be happy without a drip drip.
Good info, thanks. I will check the drive gear color.
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Old 03-05-2026, 01:54 PM   #13
r8rs4lf
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Re: Leakage through speedometer cable

Got the parts yesterday so I decided to handle it today.

Pretty easy, done in about 30 minutes unlike my fuel line debacle.

Driven gear was brown 18t with what looked like a brown drive gear inside.

I replaced the 18t with a 17t because my speedometer is a bit off. Speedometer would say 65 and I would be going 70ish according to app on phone.

One thing I did that might help others is I jacked up the rear end supported with jack stands so I would get less tranny fluid coming out. I actually only got a few drips.

Thanks again guys!
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