350c transmission leak at speedo cable. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

leftylou · Yesterday, 05:13 PM

My transmission is leaking around speedo bullet. The center o ring is sealing fine, it is leaking around the outside o ring. I have replaced the entire bullet, both o rings and the speedo gear twice and it is still leaking. I’m wondering if the o ring might be slightly under sized. Does anyone have a good source for the correct o ring? Or any other ideas why this may be leaking?

geezer#99 · Yesterday, 08:00 PM

Is the transmission vent clean?

leftylou · Yesterday, 11:47 PM

I know very little about transmissions so o have to admit I don’t know what a transmission vent is much less the condition of mine. How would the vent cause the leak around the bullet? Would the engine need to be running for this to cause a leak? The truck is currently sitting and still leaking.

**leddzepp** · Yesterday, 11:53 PM

The vent is a tube on the top of the transmission, sometimes it becomes plugged and if so will cause excessive pressure to build up, which causes a leak.

**Rust_never_sleeps** · Today, 01:12 AM

^^ if it leaks when hot, it may be the vent. If it leaks when cold, probably not

Yesterday, 05:13 PM	#1
leftylou Registered User Join Date: Apr 2022 Location: Austin Texas Posts: 36	350c transmission leak at speedo cable. My transmission is leaking around speedo bullet. The center o ring is sealing fine, it is leaking around the outside o ring. I have replaced the entire bullet, both o rings and the speedo gear twice and it is still leaking. I’m wondering if the o ring might be slightly under sized. Does anyone have a good source for the correct o ring? Or any other ideas why this may be leaking?

Yesterday, 08:00 PM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,715	Re: 350c transmission leak at speedo cable. Is the transmission vent clean?

Yesterday, 11:47 PM	#3
leftylou Registered User Join Date: Apr 2022 Location: Austin Texas Posts: 36	Re: 350c transmission leak at speedo cable. I know very little about transmissions so o have to admit I don’t know what a transmission vent is much less the condition of mine. How would the vent cause the leak around the bullet? Would the engine need to be running for this to cause a leak? The truck is currently sitting and still leaking.

Yesterday, 11:53 PM	#4
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,023	Re: 350c transmission leak at speedo cable. The vent is a tube on the top of the transmission, sometimes it becomes plugged and if so will cause excessive pressure to build up, which causes a leak. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man RIP FleetsidePaul

Today, 01:12 AM	#5
Rust_never_sleeps Senior Member Join Date: Jun 2022 Location: San Ramon,CA Posts: 569	Re: 350c transmission leak at speedo cable. ^^ if it leaks when hot, it may be the vent. If it leaks when cold, probably not __________________ 1970 C10 Custom longbed 350/350



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