M-21 lube leaking out of the speedo cable

[sixt9x33rs]

After running my car for about 20 miles in City traffic I have gear lube leaking off the speedo cable just before the cable attaches to the speedometer underneath the cluster. Any idea what would cause this? I am using Royal Purple synthetic lube. I checked the level and it is not over filled.

Thanks

[Stingr69]

I tried royal purple and it was slightly more noisy and leaked for me as well. We could argue the reasons but bottom line is I would go back to GL-4 dino 90Wt and look at replacing the O-ring on the speedo gear holder.  Leave the speedo cable attached, loosten the tiny screw that holds the retainer and swing the retainer out of the way, then use the speedo cable to pull the whole thing out so you can get the O-ring replaced.

Definately go back to the GL-4 90Wt gear oil. Synthetic is not good for the brass in your transmission. 90Wt will be quieter, it will leak less, and the brass synchro rings will be much happier.

-Mark.

[sixt9x33rs]

Thanks for the input.

[JohnZ]

There should also be a pressed-in rubber seal in the end of the speedo "bullet" where the cable ferrule screws on to keep gear lube from "climbing" the flex shaft.

[sixt9x33rs]

Thanks John I will check that.

[sixt9x33rs]

There should also be a pressed-in rubber seal in the end of the speedo "bullet" where the cable ferrule screws on to keep gear lube from "climbing" the flex shaft.

John do I have to unscrew the cable from the bullet to get to the rubber seal?

Are these parts I can buy at NAPA?

Thanks again

[JohnZ]

There should also be a pressed-in rubber seal in the end of the speedo "bullet" where the cable ferrule screws on to keep gear lube from "climbing" the flex shaft.

John do I have to unscrew the cable from the bullet to get to the rubber seal?

Are these parts I can buy at NAPA?

Thanks again

Yes - unscrew the cable ferrule from the "bullet" and you should see the black rubber seal. Don't know offhand if NAPA carries the seal separately or not. The "bullet" is called a "fitting", and is P/N 3869912 (includes the seal), in group 4.338. The seal itself is P/N 3869910.

[sixt9x33rs]

There should also be a pressed-in rubber seal in the end of the speedo "bullet" where the cable ferrule screws on to keep gear lube from "climbing" the flex shaft.

John do I have to unscrew the cable from the bullet to get to the rubber seal?

Thank you very much.

Are these parts I can buy at NAPA?

Thanks again

Yes - unscrew the cable ferrule from the "bullet" and you should see the black rubber seal. Don't know offhand if NAPA carries the seal separately or not. The "bullet" is called a "fitting", and is P/N 3869912 (includes the seal), in group 4.338. The seal itself is P/N 3869910.

[JohnZ]

Photo below shows the end of the fitting where the speedo cable ferrule screws on; if you look closely at the end of the plastic speedo gear, you can see the black rubber seal.

[jl8dale]

Awesome pic John.

I have the same problem in one of my Pace Cars with oil under my dash around the speedometer and wasn't sure why it was happening.

Thanks for your insight on this.

[click]

A few more pics of speedo leaking issue. Mine is off TH350 but same problem, leaked down onto my foot while driving on a 2500 mile trip to a car show in Seattle. Chev.dealer replaced the bullet and all the seals and O-rings, dry ever since.

[68Zproject]

A picture is worth a thousand words.  I didn't know about that one in the end of the bullet.

[sixt9x33rs]

Thanks for the pictures guys. That really helps explain the situation. Now I just need to find the time to fix it.

[sixt9x33rs]

There should also be a pressed-in rubber seal in the end of the speedo "bullet" where the cable ferrule screws on to keep gear lube from "climbing" the flex shaft.

John do I have to unscrew the cable from the bullet to get to the rubber seal?

Are these parts I can buy at NAPA?

Thanks again

Yes - unscrew the cable ferrule from the "bullet" and you should see the black rubber seal. Don't know offhand if NAPA carries the seal separately or not. The "bullet" is called a "fitting", and is P/N 3869912 (includes the seal), in group 4.338. The seal itself is P/N 3869910.

John thanks for the part numbers. NAPA had just the seal. I will intall it and see how it works

[sixt9x33rs]

John do you have another part number for the seal? What I got today at NAPA was for an automatic transmission and they did not have the part number for the bullet.

Thanks!