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Topic: Speedometer Gear

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Speedometer Gear (1/22)
 7/26/13 5:23pm
genefox
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Lake Ariel, PA - USA

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Hi, I noticed some trans fluid on my garage floor. I jacked up my vette and crawled under for a look. The fluid was dripping a few drops from the speedometer cable unit, from under the coupler nut but I also noticed that the speedometer gear that the cable hooks to is loose. It can be moved up and down and back and forth on the side of the trans case. Is there a fix for this or will it be an expensive repair? The holder for the gear is in place to retain it but the gear is visibly loose where it goes into the trans. Does anyone have any help or assistance on this matter? I am afraid to run my car too far with this problem. Help. Thank you. 
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Re: Speedometer Gear (2/22)
 7/26/13 10:25pm
dyoes
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This is not a bad fix.  If you have a stock transmission pan (without a drain plug), you'll have to remove the transmission pan to drain the fluid from the transmission.  The transmission gear housing comes out with one bolt.  There is a large o-ring around the housing, and a small (spring loaded) o-ring that surrounds the plastic gear itself.  Very cheap fix.

If you have to drop the pan, I would change the transmission filter while you've got it down.

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Re: Speedometer Gear (3/22)
 7/27/13 2:59pm
genefox
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Lake Ariel, PA - USA

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Thank you for your input, I appreciate it but what about the gear moving when you wiggle the speedometer cable/ Is something worn there or will the new "O" rings tighten up the gear where it comes out on the side of the trans. Last year when the speedometer cable broke it was twisted apart at the end that goes into the trans gear. Again I appreciate you input. 
Re: Speedometer Gear (4/22)
 7/27/13 4:59pm
dyoes
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The gear is a bit sloppy, but it shouldn't wiggle too much.  The gear looks like this:



Your gear shaft may be snapped inside of the housing.  If the speedo cable siezed up, it's possible.  But it would usually just chew up the sqare drive on the gear shaft and not break the entire gear.  Either way, inspect the gear shaft and teeth when you get it out to make sure it's not chewed up.  The gear meshes with a gear inside the transmission; if one is messed up the other may be as well.  I'm not sure how hard it is to change the gear inside the tranny, but it would scare me...  Gear inside of the transmission looks like this:



The gears are colored based on the number of teeth (makes your speedo correct for your rear end ratio).  So if you need a new one, they are about 10 bucks on eBay.  Just buy the same color.  But because transmission fluid can stain a white gear, count the teeth just to make sure.

The housing and o-rings look like this: 



The small o-ring isn't visible in this picture. 

One thing to be careful of... It is VERY possible to drop the gear in the transmission during reinstallation!  Be careful.

Let me know how you make out...




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Re: Speedometer Gear (5/22)
 7/31/13 9:35am
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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Since we are on speedo gears, I need to change mine. Doing it is no problem but what I need to know is WHAT gear do i need to put in it.
 
I have a M20 4 speed, 3:08 rear end, 295/50-15 rear tires.
when I am going 50 mph my speedo read 60. So it is off about 10 mph what ever I am driving.
Does anyone know what gear I need to put in the side? What color / teeth ?
Do I only need to replace the one gear?
Thanks.
Joe
Re: Speedometer Gear (6/22)
 8/12/13 1:00pm
corvette440hpLifetime Member
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68vet427 said: Since we are on speedo gears, I need to change mine. Doing it is no problem but what I need to know is WHAT gear do i need to put in it.
 
I have a M20 4 speed, 3:08 rear end, 295/50-15 rear tires.
when I am going 50 mph my speedo read 60. So it is off about 10 mph what ever I am driving.
Does anyone know what gear I need to put in the side? What color / teeth ?
Do I only need to replace the one gear?
Thanks.
Joe

Speedo Chart


This will get you in the ball park


You only need this one gear (Brown 18 teeth)




(modified large image to link, and added live link-aapple)
.












|UPDATED|8/12/2013 10:00:46 AM (AZT)|/UPDATED|


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Re: Speedometer Gear (7/22)
 7/31/13 11:55am
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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Cool !!!
Thanks!
I actually have a brown gear that I bought from a guy with a mess of parts and he had a bag with different gears in it.
Thanks
Will try it.
Joe
 
Re: Speedometer Gear (8/22)
 7/31/13 12:45pm
DaveMLifetime Member
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genefox said: what about the gear moving when you wiggle the speedometer cable



The housing with the cable end in it, that bots to the trans is loose because it moves to allow for different size gears, swing the housing so the gear is in mesh with the gear in the trans and tighten down the bolt.
Dave


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Re: Speedometer Gear (9/22)
 7/31/13 12:57pm
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Duncanville, TX - USA

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I been kinda watching this thread, and so far, I haven't seen anyone ask what trans the car has...LOL
A '77 L48 should have a 350 trans. The l82 had the 400 trans. Both take different speedo housings & gears.
The 400 uses the large housing posted above, and if that thing is loose, there's a problem...
The 350 uses the small, "bullet" housing, and those can normally be wiggled around some. Here is the bullet, speedo gear, retainer, and bolt that holds it all in.








We really need to know exactly WHAT it is that is moving around, since you can't actually grab the speedo gear on either one.

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Re: Speedometer Gear (10/22)
 7/31/13 5:48pm
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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Posts: 364

also, do I need to drain the 4 speed tranny to change this?
or do I just take it out, let it drain by itself and refill when done.
Thanks again and in advance!!
Joe
Re: Speedometer Gear (11/22)
 7/31/13 7:29pm
genefox
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Lake Ariel, PA - USA

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I am guessing from your description that my L48 has a "350" trans. The car just turned 20,000 original miles last month, so everything must be stock. What I meant by wiggling is that if I am under the car and I take hold of the speedometer cable near where it attaches to the side of the trans & that the gear and cable does move up and down, not a lot, but I thought it should be tight and not move at all. I am concerned that maybe I should not be driving the car with it in that (what I call) loose condition . There is a small drip of fluid that comes out between the speedometer coupler nut  and the  speedometer cable housing. Plus I was wondering if this is going to be an expensive repair. I thank everyone for their assistance and input.
The speedometer works fine before the old cable broke and after I had the old cable replaced when it broke last summer. If you need anymore info please let me know. Again, thank you.
 
Re: Speedometer Gear (12/22)
 7/31/13 10:35pm
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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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Lake Ariel, PA - USA

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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.
 
genefox
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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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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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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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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Re: Speedometer Gear (20/22)
 8/13/13 3:14pm
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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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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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
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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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