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Topic: Speedo tranny leak

in Forum: C3 Driveline Components


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Speedo tranny leak (1/4)
 7/10/12 11:12am
r-rmiller86
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Clarksville, TN - USA

Vette(s):
1976 Black /Black Interior L48 350.


Joined: 9/23/2008
Posts: 3

I noticed last night that my tranny was leaking from the speedo cable.  I haven't taken a cable from the transmission in a while.  I believe that it is held in place with a clip that is bolted in (I can't find my manual either).  Doe the speedometer cable bullet just pull out when I remove the cable?  I haven't ever removed the bullet before and am looking for some help.  I think I am on the right track with my thinking, just not sure.  Any and all help would be appreciated!!
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Re: Speedo tranny leak (2/4)
 7/10/12 12:25pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

4 speed or automatic?
The four speeds have a small "bullet" that the speedo cable screws on to. There are two seals on the bullet. One "o-ring" on the outside of the bullet to seal it to the trans case, and one lip type seal in the inside, to seal the bullet to the speedo gear. Either one(or both) could be leaking. The bullet is held to the trans with a small clip, as you say, and there is a 7/16" head bolt that holds the clip. You can loosen the bolt, and slide the clip around to remove the bullet, but first unscrew the cable. The speedo gear will come out with the bullet. From there, you can replace both the o-ring, and the lip seal, and then reassemble.
The 350 automatic has a similar bullet, but it will be aluminuminum, instead of steel. The steel bullets usually have a metal-clad inner seal, while the aluminuminum bullets use a plain rubber seal. Both are replaceable.

      

The 400 automatic has a different housing, but the removal is basically the same, the inner seal is the same, but the outer o-ring is a larger diameter.




btw...most 4 speeds have a 90 degree adapter that the speedo cable screws onto, then the adapter screws onto the bullet. The seal replacement is the same, regardless.


|UPDATED|7/10/2012 9:25:09 AM (AZT)|/UPDATED|


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Joel Adams
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Re: Speedo tranny leak (3/4)
 7/10/12 1:39pm
r-rmiller86
Former Member

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Clarksville, TN - USA

Vette(s):
1976 Black /Black Interior L48 350.


Joined: 9/23/2008
Posts: 3

The trans is an automation thm350.  I guess I should've added that the first time.  Will the steel bullet fit the 350?  Will trans shops have the bullets on hand and sell them?


|UPDATED|7/10/2012 10:39:36 AM (AZT)|/UPDATED|
Re: Speedo tranny leak (4/4)
 7/10/12 4:52pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

Yes to both of your questions. Your 350 may have a steel bullet, but most likely it is aluminuminum..it may have been replaced somewhere down the line. The aluminuminum ones have a tendency to wallow out the hole in the center from the speedo gear spinning around in it.That causes them to leak, and sometimes, depending on how bad it is, could cause the speedo to jump.
The steel bullets are around $5-$6... at least that's what I get them for. New ones will come with the inner seal already installed. Some have the outer o-ring, but some may not. Thumbs Up

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Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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