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Topic: Speedometer Gear

in Forum: C3 Driveline Components


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Re: Speedometer Gear (12/22)
 7/31/13 10:35pm
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


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If your trans has the small, bullet type housing, they can be a little loose...not really much to hold them tight. There are two seals...an o-ring around the outside of the bullet, and the seal that seals the gear itself. You can loosen the 7/16" bolt that holds the small tab/bracket on, and let it flop down. Then, the bullet will pull right out. You might loose a couple of drops of fluid... not much, but have a drain pan, or something to catch what does drip out. 
The o-ring fits around the outside of the bullet, and changing it is just remove/replace.
The inner seal, depending on what type is has, will be a little more challenging. There are a couple of different style of seals for that. Originally, is should have a metal clad seal. Changing it requires prying it out with a small screwdriver. Replacing the metal clad seal requires a small socket, that will just fit down inside the hosing, where the seal fit. Place the seal in the housing, and use the socket, and small hammer to tap the seal down until it stops. That's it.

Most replacement seals, and later model original seals are just rubber....no steel. They are held into the housing with a small, round, metal clip. A small screwdriver will pop it right out, and the seal after that. Installation is just the reverse...seal, then clip. On the rubber seals, you have to be careful to not push it down in the housing too far, as it will distort, and not seal well.

In the last pic I posted above, you can see the inside seal. This is the seal that the speedo gear ride in. You must check the end of the plastic gear, where it rides ont he seal, because the seal, regardless of the type of seal it is, can wear the gear down,a nd put a groove in it. If the gear has a groove, the seal will not seal, and it will leak....the gear will need to be replaced.
Also, if your speedo bullet is aluminuminum, you'll need to remove the gear, and look down into the hole, where the gear runs. If the bore is egg-shaped, the bullet will need to be replaced. 

It's not really hard to fix the leak...just a couple of seals, and maybe 30 minutes of time. Thumbs Up


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Re: Speedometer Gear (13/22)
 8/1/13 8:05pm
genefox
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Thank you so much for your input but I will ask one more question. Could you resend the photos you stated to have sent? I would really appreciate it or send it to my e-mail at itsonlywarm4me@socantel.net. Again thank you for your time and input. It is appreciated.
 
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Re: Speedometer Gear (14/22)
 8/12/13 12:28pm
68vet427
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macedon, NY - USA

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68 COUPE 454 HAS MOTION HOOD SCOOP, REVERSED GILLS ZL-1 FENDER FLARES AND MOTION REAR SPOILER, LEMAN'S GAS CAP, BUCKET HEADLIGHTS. CAN-AM FRONT RACING SPOILER. CHROME HOOKER HEADERS AND SIDE PIPES! 4 SPEED M20, LOOKS FAST STANDING STILL !!


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Hi again,
OK so I finally got around to changing out the gear.
When I pulled the old one out it was a brown one. But I still put a new brown one in anyways hoping to see a differance. Confused
But, took her for a drive and it is the same, no change.
 
So with a brown gear and my speedo still is running about 10mph faster than what it should.
What do you think I should try next?
Thanks.
Joe
Re: Speedometer Gear (15/22)
 8/12/13 1:20pm
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Duncanville, TX - USA

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#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


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Only thing you CAN do, Joe...change the diff ratio...... LOL LOL

Just kiddin!
You cannot go any further with the gear changes unless you remove the trans, and change the DRIVE gear...you would need to have a drive gear with fewer teeth, and a driven gear with more teeth. However....does your trans still have the 90 degree adapter on the speedo cable, at the trans? It should have one, but if it does not, you need to get one that will slow the speedo down. Those 90 degree adapters are not simply 90 degree adapters...they also change the in/out RATIO, so the speedo will read correctly. It's much easier to spec an adapter than stock 10 different transmissions with different speedo gears, so GM used the adapters. If you DO have the adapter, then it's as easy as finding out what ratio it is, and getting one with a different ratio. The adapters are all stamped with the ratio on them, close to where the cable screws on. If no ratio change was need for that particular engine/trans/diff combo, the adapter would say "1:1". If it was a ratio change, it would read something like ".42".
btw...this info is ONLY for the 4 speed cars....the automatics did not use the 90 deg ratio adapter.

The adapter looks similar to this one....



|UPDATED|8/12/2013 10:20:26 AM (AZT)|/UPDATED|


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Re: Speedometer Gear (16/22)
 8/12/13 2:20pm
68vet427
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macedon, NY - USA

Vette(s):
68 COUPE 454 HAS MOTION HOOD SCOOP, REVERSED GILLS ZL-1 FENDER FLARES AND MOTION REAR SPOILER, LEMAN'S GAS CAP, BUCKET HEADLIGHTS. CAN-AM FRONT RACING SPOILER. CHROME HOOKER HEADERS AND SIDE PIPES! 4 SPEED M20, LOOKS FAST STANDING STILL !!


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Joel, thanks.
I checked several sites, I found the 90 degree fittings but nothing that could change my ratio.
Where can these be purchased?
Thanks.
Joe
 
Re: Speedometer Gear (17/22)
 8/13/13 12:30pm
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Duncanville, TX - USA

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#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


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Not sure who would have them, Joe, but they are available. I know of at least one place that can custom make one any ratio you need. If you take a look at the speedo chart Larry posted above, you'll notice in the far right column it says "Adapter", and will list the part number needed for that particular gear/tire ratio, to make the speedo correct. Doesn't really apply to you, but just wanted to point out that they were factory installed in certain circumstances.
I'll see if I can dig up the info on the place I'm tinkin aboot, and post it here. The last 700 swap I built for a local guy needed one, and he had one made....I'll see can I find the info. Thumbs Up

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Re: Speedometer Gear (18/22)
 8/13/13 12:45pm
68vet427
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macedon, NY - USA

Vette(s):
68 COUPE 454 HAS MOTION HOOD SCOOP, REVERSED GILLS ZL-1 FENDER FLARES AND MOTION REAR SPOILER, LEMAN'S GAS CAP, BUCKET HEADLIGHTS. CAN-AM FRONT RACING SPOILER. CHROME HOOKER HEADERS AND SIDE PIPES! 4 SPEED M20, LOOKS FAST STANDING STILL !!


Joined: 7/20/2006
Posts: 364

Joel, Thanks.

I will also continue to look.
Joe
 
Re: Speedometer Gear (19/22)
 8/13/13 2:47pm
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Duncanville, TX - USA

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#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


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Joe, I think this is the place my buddy got his adapter, but not 100% sure. They DO have some NOS Gm adapters in stock, and can build a different type(not 90 degree) if needed. Might give them a shout and see if they can help ya.


APT Instruments

They also show how to Check the Ratio  Big smile


|UPDATED|8/13/2013 11:47:36 AM (AZT)|/UPDATED|


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Joel Adams
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Re: Speedometer Gear (20/22)
 8/13/13 3:14pm
68vet427
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macedon, NY - USA

Vette(s):
68 COUPE 454 HAS MOTION HOOD SCOOP, REVERSED GILLS ZL-1 FENDER FLARES AND MOTION REAR SPOILER, LEMAN'S GAS CAP, BUCKET HEADLIGHTS. CAN-AM FRONT RACING SPOILER. CHROME HOOKER HEADERS AND SIDE PIPES! 4 SPEED M20, LOOKS FAST STANDING STILL !!


Joined: 7/20/2006
Posts: 364

AWESOME! THANKS!
I will have to try the easy method. will probably jump on the NYS thruway, it is fairly straight. I will let you know when I get the results.
Joe
 
Re: Speedometer Gear (21/22)
 8/14/13 7:37am
chronos51
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Phoenix, AZ - USA

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1982 corvette crossfire production numer C5101985. Color is silver and claret. All original numbers match. slight mods to crossfire for better efficiancy and power balanced and added fuel pressure assembly between throttle bodies,


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Since the Speedometer gear is being talked about, on my 82 the speedometer bounces and squeaks most of the time, occasionally it will stop squeaking but it still bounces, I am not sure how to correct this, 
do I need to replace the cable? tighten it at the head unit or tranny? its a really annoying squeak and since i dont have my stereo fully hooked up i cant drown the noise out while driving...LOL
thanks in advance for the assistance 


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Re: Speedometer Gear (22/22)
 8/14/13 1:46pm
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

I would first suggest removing the cable, and lubing it. Do the upper and the lower cable. If that does not take care of the squeak, the noise is in the speedo head. Ouch

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Joel Adams
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