Powerglide Parts Source

[Joe M.]

Where would I find a new speedometer gear retainer or "bullet" for a 1960 cast iron PG?

I have looked on multiple web sites, but have not found a new bullet; plastic gears, yes.

[Joe L.]

Re: Powerglide Parts Source

Where would I find a new speedometer gear retainer or "bullet" for a 1960 cast iron PG?

I have looked on multiple web sites, but have not found a new bullet; plastic gears, yes.

Joe------


That's a tough one. The speedometer driven gear FITTING ("bullet") for your application was GM #3708147. However, it was discontinued without supercession in July, 1977.

The strange thing is that a fitting for 1961+ Powerglide applications remains available from GM. I believe the difference is length. The 3708147 was 2-5/8" overall length. The later fitting is 1-7/8" overall length.

[Edward M.]

Re: Powerglide Parts Source

Isn't this the same part that would be on any Powerglide of that vintage. As I recall, it is not Corvette specific, a passenger car "bullet" would work.

[Joe M.]

Re: Powerglide Parts Source

Joe, you are correct, the difference in the later year PG bullets is the length; they are shorter. I found numerous new PG bullets for sale, but they are for the aluminum PG.

I spoke at length with Tom Ambrose about the issue and he was skeptical about the ATF leaking around the driven gear and out the speedo cable. He said in his experience, the problem was the exterior o-ring. Easy way to test is install the new o-ring, and put the bullet back in place, but leave speedo cable off, fill PG with ATF, and see if that stops the leak or if it is coming through the bullet. The exterior o-ring was deteriorated to the point that it did not look like rubber. It was a ring of flattened mush.

I will try that before I replace the bullet and driven gear. Tom has new bullets for sale if I need one.

[Joe L.]

Re: Powerglide Parts Source

Isn't this the same part that would be on any Powerglide of that vintage. As I recall, it is not Corvette specific, a passenger car "bullet" would work.

Ed------


Yes, it's the same as passenger car but only up to 1960. After 1960 the shorter fitting was used for both Corvette and passenger car.

[Joe L.]

Re: Powerglide Parts Source

Joe, you are correct, the difference in the later year PG bullets is the length; they are shorter. I found numerous new PG bullets for sale, but they are for the aluminum PG.

I spoke at length with Tom Ambrose about the issue and he was skeptical about the ATF leaking around the driven gear and out the speedo cable. He said in his experience, the problem was the exterior o-ring. Easy way to test is install the new o-ring, and put the bullet back in place, but leave speedo cable off, fill PG with ATF, and see if that stops the leak or if it is coming through the bullet. The exterior o-ring was deteriorated to the point that it did not look like rubber. It was a ring of flattened mush.

I will try that before I replace the bullet and driven gear. Tom has new bullets for sale if I need one.

Joe------


I would replace the seal on BOTH the perimeter of the fitting (i.e. O-ring) as well as the seal on the inside of the fitting. I highly doubt that you need a new fitting. I can't really see what sort of wear or damage could occur to the fitting.

[Joe M.]

Re: Powerglide Bullet

Joe, I am not sure what fitting seal you are talking about.

The bullet has an external o-ring around the center and the only seal the steel speedo cable makes is metal to metal when it is screwed into the male end of the bullet. What fitting and seal are your referring to? Approximately half way down the bore of the bullet, the diameter increases towards the speedo cable end of the bullet; maybe 1/32" larger from that point to the end. There is a lip in the center of the bore. The bore is slightly larger from that point to the speedo end of the bullet. I wondered if there was at one time a seal pushed down the bore and resting at the change in diameter. Since I have never seen a new bullet, I don't know.

I ordered a new driven gear today; figured the diameter of the shaft had to be worn down some and maybe fluid was leaking around the gear and out the end of the bullet. Several unknowns at this point.

[Joe L.]

Re: Powerglide Bullet

Joe, I am not sure what fitting seal you are talking about.

The bullet has an external o-ring around the center and the only seal the steel speedo cable makes is metal to metal when it is screwed into the male end of the bullet. What fitting and seal are your referring to? Approximately half way down the bore of the bullet, the diameter increases towards the speedo cable end of the bullet; maybe 1/32" larger from that point to the end. There is a lip in the center of the bore. The bore is slightly larger from that point to the speedo end of the bullet. I wondered if there was at one time a seal pushed down the bore and resting at the change in diameter. Since I have never seen a new bullet, I don't know.

I ordered a new driven gear today; figured the diameter of the shaft had to be worn down some and maybe fluid was leaking around the gear and out the end of the bullet. Several unknowns at this point.

Joe-----


There is (or, should be) a seal that is pressed down into the bore of the fitting (from the threaded end). The 1961+ fittings definitely have this seal and, as far as I know, the earlier fittings do, too. This is a very small lip seal with metal frame (like a miniature wheel bearing seal). You can obtain one under GM #3869910. The seal is not obvious when you look at the threaded end of the fitting, but it should be there.

[Joe M.]

Re: Powerglide Parts Source

I can see the lip inside the bore and assumed some type of seal used to be there, but could not get a confirmation until now. Thank you.

Chevy dealers still carry the lip seal? I believe with the new lip seal, new o-ring and new driven gear, the leak should be fixed.

[Joe L.]

Re: Powerglide Parts Source

I can see the lip inside the bore and assumed some type of seal used to be there, but could not get a confirmation until now. Thank you.

Chevy dealers still carry the lip seal? I believe with the new lip seal, new o-ring and new driven gear, the leak should be fixed.

Joe-----


If it doesn't fix it, I don't think a new fitting will fix it, either. The fitting is really not a wear part. The other components are.

[Ray K.]

Re: Powerglide Parts Source

Joe -- Joe

It is my recollection that neither of the early long ( 2 5/8 ) speedo fittings #3708147 and #3748533 were machined for a lip type seal at the cable attachment end. The only seal was for the o'ring #3708146. I think the o'ring was located in a slightly different position for these two fitting numbers. The lip seal for the cable attachment end did not appear until the 1965 catalogs as #3869910. This seal was installed in the new shorter
( 1 7 /8 ) speedo fitting #3869912 and #3869914. I can not say for sure when production vehicles actually started using the later style fitting with the additional seal at the the cable end.

Ray

[Joe L.]

Re: Powerglide Parts Source

Joe -- Joe

It is my recollection that neither of the early long ( 2 5/8 ) speedo fittings #3708147 and #3748533 were machined for a lip type seal at the cable attachment end. The only seal was for the o'ring #3708146. I think the o'ring was located in a slightly different position for these two fitting numbers. The lip seal for the cable attachment end did not appear until the 1965 catalogs as #3869910. This seal was installed in the new shorter
( 1 7 /8 ) speedo fitting #3869912 and #3869914. I can not say for sure when production vehicles actually started using the later style fitting with the additional seal at the the cable end.

Ray

Ray------


I'm not sure, either about the lip seal for the early style fitting. I have conflicting information on it.

[Joe M.]

Re: Powerglide Parts Source

i am going to order the lip seal from Chevy on Monday; $8.50. I asked what the part description was and parts man said "seal." Since my short bullet has a lip inside the bore at the mid point, I am willing to spend $8.50 to see if it is correct. I believe it will be. The lip was not milled inside the bore for no reason. New 21 tooth red driven gear is ordered and on the way.

[Joe L.]

Re: Powerglide Parts Source

i am going to order the lip seal from Chevy on Monday; $8.50. I asked what the part description was and parts man said "seal." Since my short bullet has a lip inside the bore at the mid point, I am willing to spend $8.50 to see if it is correct. I believe it will be. The lip was not milled inside the bore for no reason. New 21 tooth red driven gear is ordered and on the way.

Joe------


I hope you're not going to be buying something you can't use. The more I research this, the more I doubt that a seal was used on the early style fittings. If it was used, it was not available as a separate part at that time. That's very possible, though. I can tell you that GM shows the applicability of the 3869910 seal to include 1957-81 for manual trans applications. However, the same fitting used for 1957-60 Powerglide applications was also used for some manual transmission applications.

In any event, the 3869910 is a seal with a metal outer frame of about 3/8" OD and about 3/16" thick. So, the counterbore in your fitting (into which the seal is pressed) would have to be large enough to accommodate this.

[Joe M.]

Re: Powerglide Part

i am listening to you Joe and taking measurements. I believe you saved me a trip to the Chevy parts counter and $9.00! i used digital calipers and obtained the following:
The I.D of the counterbore is 0.36" (on the end closest to the speedo fitting)
diameter of seal is 0.375" (3/8")

The GM seal will not fit into the counterbore.

I will install the new driven gear and install the bullet with new exterior o-ring and see what happens.

Thanks Joe for continuing to dig into my issue and providing the final answer.