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Old 12-20-2025, 05:45 PM   #1
Loose Screw
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TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Yeah I got a leak. Been under the truck a few times and watched a bunch of YouTubes. Pretty sure This is what I'm needing....
Ebay China stuff, pretty much the norm nowadays...

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Old 12-20-2025, 05:53 PM   #2
geezer#99
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

There are better places to shop than on eBay.

https://transmissioncenter.net/
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Old 12-20-2025, 06:45 PM   #3
Shark_13
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

I replaced the outer o ring on mine and it stopped leaking.
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Old 12-26-2025, 08:06 PM   #4
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Typically, it's the plastic stem that has a groove worn into it where the seal rides. It requires the replacement of the nylon gear and the seal.

The speedometer cable is not meant to stop any leaks it should be hand-tightened only.
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Old 12-26-2025, 09:42 PM   #5
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Quote:
Originally Posted by geezer#99 View Post
There are better places to shop than on eBay.

https://transmissioncenter.net/
I have searched that site a number of times and can not find any of the replacement speedometer gears. Maybe someone who knows how to type can confirm that they have those available for TH30/400.
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Old 12-26-2025, 11:17 PM   #6
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

https://www.speedwaymotors.com/Speed...IaAsV8EALw_wcB
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Old 12-26-2025, 11:48 PM   #7
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Any well equipped transmission shop will have what you need.. I get my transmission parts from Palestine Transmissions in Palestine Texas..

The gear color denotes the tooth count. At most, you'll need a gear (proper color) the small seal and one O-Ring..
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Old 12-26-2025, 11:50 PM   #8
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Quote:
Originally Posted by Orange Crate View Post
I have searched that site a number of times and can not find any of the replacement speedometer gears. Maybe someone who knows how to type can confirm that they have those available for TH30/400.
You are correct.
Maybe they downsized, got rid of the small parts.
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Old 01-03-2026, 06:08 PM   #9
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

subscribed.
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Old 01-03-2026, 07:28 PM   #10
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

I had this issue last summer. I could not get the right gear needed for my tire size after my aftermarket adaptor failed. I am sorry I did not keep notes. Here is the issue. There are 2 diameter size drive gears that slide on the output shaft of the tranny that does nothing but drive the speedo gear. Each diameter drive has multipal tooth count to blend with mated diameter speedo gear. So it's no issue to swap if need be as I did. One of the sized drive gears from the factory has all the speedo gears needed to cover most tire ranges. The other output gear is void of newly manufactured product and many of the matching speedo gears are NLA and hard to find any good used ones. I eventually gave up on the search for the needed speedo gear for the drive I had and swapped in the more common sized drive gear and the result was perfect. Also, swapping the drive gear on the output shaft is a 30 minute job. Don't stress it as I did, really simple procedure.

Last edited by PbFut; 01-03-2026 at 10:52 PM.
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Old 01-03-2026, 07:55 PM   #11
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Another culprit to inspect while you’re down there is the gear selector shaft seal. About $13.50 on Amazon, includes a tool for the removal and installation. Be careful slipping the new seal on, that shaft can damage the new seal if you’re not careful 🤣.
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Old 01-03-2026, 08:04 PM   #12
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Quote:
Originally Posted by SRU1436 View Post
This makes a lot of sense
Summit has all the parts, but by the time I select a gear and bullet, I'm less than $10 from this kit price
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Old 01-05-2026, 11:51 AM   #13
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

I've used these guys in the past with good results.

https://classictransmissionsolutions...-350-2/?page=1
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Old 01-05-2026, 12:57 PM   #14
Loose Screw
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Re: TH350 Automatic Transmission Speedometer Cable Bullet & Gear

Yeah, I just replaced the "Bullet", gaskets and gear with the eBay part (s)...D*mn, I think the hold down bolt hole on the casing is stripping.
I'll check to see today if the leak stopped, the Bullet still seems awfully loose though....

Update: Checked It, Looks* like I'm good...We'll see!

Last edited by Loose Screw; 01-05-2026 at 02:34 PM.
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