C2 Tranny Speedo Gear Fitting

[James W.]

I am in the process of purchasing a new speedometer gear fitting that mounts in the transmission for my '64 Corvette. I had planned to order it from C Central, but there catalog says this parts is for 1965 to 1967 Muncie transmissions. The GM part number that they gave me is #345215 and is valid for Muncie transmissions up to 1981. My question is this the correct part number for my car or was there a change from the mid 1963/'64 to '65 Muncie transmissions? Zip Products and Paragon also have this item listed in their catalogs and include the 1963/64 model year. Have I just answered my own question?

Best Regards,

James West
NCRS #18379
1964 Corvette #9258

[Mike M.]

Re: C2 Tranny Speedo Gear Fitting

are you referring to the speedometer DRIVE gear that slips on the tailshaft or the speedometer DRIVEN gear housing that slips in the tailshaft housing?

[James W.]

Re: C2 Tranny Speedo Gear Fitting

Mike,

I'm referring to the speedo driven gear housing that fits into the tailshaft housing. I believe that mine is faulty since I'm getting gear lube up in the speedo head assembly via speedo cable rotation drawing it up there.

James West

[Duke W.]

Re: C2 Tranny Speedo Gear Fitting

The part you are referring to is called a "fitting", Group 4.338. My P&A catalog shows one for 1960 only, and 345215 for 65-75 w/Muncie.

There's obviously a gap here - another parts book omission/error.

Maybe Joe can sort this out.

According to the note the 345215 fitting inlcudes a seal, which probably refers to a seal on the ID. There is also a "seal" on the OD - an O-ring - but it's not clear from my catalog, which of the four listed seals in this group is correct.

If you're going to replace the fitting, I'd definitely recommend replacing the O-ring seal that seals the OD of the fitting to the transmission extension housing.

Duke

[James W.]

Re: C2 Tranny Speedo Gear Fitting

Duke,

I've already got the o-ring seal for the OD of the fiting. I just want to be sure I buy the correct fitting. As you describe the internal seal of my original fitting is faulty and has allowed gear lube to migrate up into the speedo head. I'm having the speedo head cleaned and checked before reinstalling it. I'd like to be sure I have the problem fixed.

Thanks,

James West

[Joe L.]

Re: C2 Tranny Speedo Gear Fitting

James-----

The GM #348215 fitting will service your application perfectly. It is also virtually identical to the original fitting used for your car. However, as far as I know, neither the original fitting nor the 345215 has any sort of an internal seal or o-ring. There is the external o-ring seal which provides the seal from the fitting to the extension housing, but no seal between the fitting bore and the speedo driven gear.

[Wayne K.]

Re: C2 Tranny Speedo Gear Fitting

James,

Many years ago I had this same problem with a 70 LT-1 I had at the time and I fixed it by replacing the inner seal and the driven gear. As I remember the plastic gear gets a slight grove worn in it where it makes contact with the seal but it is enough that the oil makes its way past and continues up the cable. I think that replacing the seals and the driven gear could fix your problem.

[Joe L.]

Correction

I was incorrect regarding the inner seal on the speedometer driven gear fitting. There is an inner seal. It's not an o-ring, though. It's a very small, metal frame lip seal. This seal can be replaced seperately and is available under GM #3869910.

[James W.]

Re: Correction

Mike, Wayne, Duke and Joe,

Thanks for all of your input. I'll order the new inner seal and dive under the car to see what color my speedo driven gear is. As I remember, for a 3.36:1 rear end ratio, the gear should be a 20 tooth (blue) one. I'll spend another $9.00 if that will fix the problem.

Thanks again guys, I really appreciate you help.

Best Regards,

James West
Omaha, NE.
NCRS #18379
1964 Corvette #9258

[Ed S.]

Re: Correction - Powerglide Seal Also?

Joe,

Does the speedometer fitting housing also contain a similar inner seal on a original '66 Powerglide? If so, do you have the part number for the seal or entire fitting assembly?

I'm experiencing ATF leakage from inside the speedo cable, but couldn't see a inner seal or any visible signs of wear on the metal fitting or plastic speedo driven gear when I had them removed to replace the outer o-ring seal on the fitting.

I do have a new plastic speedo driven gear on hand to try next.

TIA,
Ed

[Joe L.]

Re: Correction - Powerglide Seal Also?

Ed-----

1961-67 Powerglide uses the same fitting and seal as previously described.