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?

Re: 350c transmission leak at speedo cable.
 

Is the transmission vent clean?

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.

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.

Re: 350c transmission leak at speedo cable.
 

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

Re: 350c transmission leak at speedo cable.
 

It’s leaking when cold. I guess I need to try a third o ring unless anyone knows any trick to get this one to seal better.

Re: 350c transmission leak at speedo cable.
 

Post a pic of the speedo bullet.

Re: 350c transmission leak at speedo cable.
 

Here’s a photo. The original is on top, the new one is on bottom.

Re: 350c transmission leak at speedo cable.
 

If the bullet pushes in with a little resistance the O ring is likely ok.
There is a lip seal on the gear. Typically they wear a groove in the plastic gear.
Was the gear new. Worked on 100s of these and never had the large O ring leak.
How about some pictures of both gears? It’s almost always the seal or gear stem seal.

Re: 350c transmission leak at speedo cable.
 

I replaced the gear both times I replaced the bullet so there shouldn’t be a groove worn in it. I’m pretty sure it’s leaking around the outside of the bullet but I will look again. I will also try putting the new o ring on the old bullet, maybe the new one is slightly smaller. Do you mean pictures of the gear outside of the bullet?

Re: 350c transmission leak at speedo cable.
 

O-ring kits are cheap.
Here’s an example.

https://www.canadiantire.ca/en/pdp/d...w.ds#store=488

Re: 350c transmission leak at speedo cable.
 

U should feel the o ring squish. It’s a confirmation the o ring is the correct size.
Some builders use a dab of silicone after cleaning all the oil off everything. .
That should fix it.

Re: 350c transmission leak at speedo cable.
 

Thanks, I might try the silicone.