John Z
Thread Starter
Racer
Joined: Aug 2003
Posts: 404
Likes: 0
From: Sitka Alaska
John Z
Where can I find the speedometer correction box that you mentioned in an earlier post? The only one I found is for new model electronic speedometers. My car is a 61, changing rear gears from 3.36 to 4.56, where I live (on an island in the gulf of Alaska) there are no speed shops so need a phone number, web site, or e-mail address if you could please.
Thanks,
EVERGREEN
Thanks,
EVERGREEN
Safety Car
Joined: Aug 2000
Posts: 4,148
Likes: 642
From: Bandera Texas
Re: John Z (EVERGREEN)
There is a plastic gear that goes into the side of the transmission and then the speedo cable is screwed into that. Different color gears that have different numbers of gear teeth are used for different rear end ratios.
Go to http://www.corvettecentral.com and ask them for the proer gear. I do not know the color or number of teeth, but they have serviced this part in the past.
[Modified by jimgessner, 10:45 AM 12/31/2003]
Go to http://www.corvettecentral.com and ask them for the proer gear. I do not know the color or number of teeth, but they have serviced this part in the past.
[Modified by jimgessner, 10:45 AM 12/31/2003]
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Safety Car
Joined: Aug 2000
Posts: 4,148
Likes: 642
From: Bandera Texas
Re: John Z (paul67)
THANKS PAUL
BASED ON THAT AND NOT KNOWING WHAT SIZE TIRE,I WOULD GUESS THE 17 TOOTH PURPLE IS WHAT CHEVY WOULD RECOMEND WITH A 4:56 REAR GEAR.
[Modified by jimgessner, 11:41 AM 12/31/2003]
BASED ON THAT AND NOT KNOWING WHAT SIZE TIRE,I WOULD GUESS THE 17 TOOTH PURPLE IS WHAT CHEVY WOULD RECOMEND WITH A 4:56 REAR GEAR.
[Modified by jimgessner, 11:41 AM 12/31/2003]
Racer
Joined: Dec 2002
Posts: 437
Likes: 54
From: Cincinnati Ohio
Re: John Z (66427-450)
________________________________________ _____________________
Guys -
He's looking for the "box"......... so he doesn't have to change the gear inside the Trans
________________________________________ _____________________
It is not inside the transmission. It is where the speedo cable goes into the transmission and is held in place by a small bolt. It slips out very easily.
Dave
:cheers:
Guys -
He's looking for the "box"......... so he doesn't have to change the gear inside the Trans
________________________________________ _____________________
It is not inside the transmission. It is where the speedo cable goes into the transmission and is held in place by a small bolt. It slips out very easily.
Dave
:cheers:
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Re: John Z (jimgessner)
If the poster could give us the tire size, we could determine the revs/mile and come down to the correct driven gear. The change in the rear axle is so drastic, however, that he may have to go with a new transmission drive gear as well as the driven gear.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Re: John Z (paul67)
The question is where the poster can find the "external" box (adapter) that can be used to correct the speedometer reading, not the source for the "internal" gears in the transmission. There is an adapter (box) that can be installed external to the transmission and the speedometer head that will change the speed of the exit cable relative to the speed of the entrance cable. Sorry, but I can't supply a source. I've also been looking for one.
Racer
Joined: Dec 2002
Posts: 437
Likes: 54
From: Cincinnati Ohio
Re: John Z (JoesC5)
Below is an image of the part that needs to be replaced and it is called the "Driven Gear". It is the nylon colored gear in the top left of the picture. It is held by the bullet shaped item next to it that is held in the transmission by a small bolt and a clip. The "Driven Gear" is run by the ring shaped gear that is in the lower right of the picture. This gear goes around the output shaft in the tail of the transmission. A 4.56 driven gear can be purchased from LIC for $12.50 part # 32-64D.
Dave
:cheers:
[Modified by Dave McDufford, 5:47 PM 12/31/2003]
Dave
:cheers:
[Modified by Dave McDufford, 5:47 PM 12/31/2003]
Race Director
Joined: Nov 2000
Posts: 10,340
Likes: 664
From: Beverly Hills (Pine Ridge) Florida
Re: John Z (JoesC5)
Evergreen,
I understand what you are talking about! I have an old one in stock. They are used in situations where you do not want to replace the driven gear (as described by Dave above). They mount to the speedo output on the trans, and then the speedo cable connects to this gear box. The gear box has a gear reduction to correct for the "wrong" driven gear. The trans driven speedo gear still needs to be corrected, but at least it is now within "range".
These external speedo gear boxes were available from GM Dealers a few years ago. Probably no longer available, but it would not hurt to call up Scroggins-Dickey http://www.sdpc2000.com/ to see if they know where you can get one, or contact your "local" GM dealer (where ever that may be!). Other option is to contact a Speedo repair service (if any are still in business). We have one in this area, and I can check to see if they have one available (but not until Friday - best send me an E-Mail reminder! - to wake me up after the next two days).
Plasticman
[Modified by Plasticman, 5:00 PM 12/31/2003]
I understand what you are talking about! I have an old one in stock. They are used in situations where you do not want to replace the driven gear (as described by Dave above). They mount to the speedo output on the trans, and then the speedo cable connects to this gear box. The gear box has a gear reduction to correct for the "wrong" driven gear. The trans driven speedo gear still needs to be corrected, but at least it is now within "range".
These external speedo gear boxes were available from GM Dealers a few years ago. Probably no longer available, but it would not hurt to call up Scroggins-Dickey http://www.sdpc2000.com/ to see if they know where you can get one, or contact your "local" GM dealer (where ever that may be!). Other option is to contact a Speedo repair service (if any are still in business). We have one in this area, and I can check to see if they have one available (but not until Friday - best send me an E-Mail reminder! - to wake me up after the next two days).
Plasticman
[Modified by Plasticman, 5:00 PM 12/31/2003]
Safety Car
Joined: Mar 2002
Posts: 3,780
Likes: 442
From: Southwest MI
Re: John Z (Dave McDufford)
Below is an image of the part that needs to be replaced and it is called the "Driven Gear". It is the nylon colored gear in the top left of the picture........
Racer
Joined: Dec 2002
Posts: 437
Likes: 54
From: Cincinnati Ohio
Re: John Z (66427-450)
________________________________________ ______________________
understand there are two gears that must be considered if you want to set it up correctly. the plastic "driven gear" you are refering to, and the "drive gear"...... the one that drives the driven gear. they used 2 different drive gears in the Muncie's, i believe a 6 tooth for the 4.56, and a 8 tooth for the higher gear sets.
________________________________________ ______________________
You are correct. I looked in the part manual and it is rather confusing :confused: . I could not figure out which was which.
Dave
:cheers:
understand there are two gears that must be considered if you want to set it up correctly. the plastic "driven gear" you are refering to, and the "drive gear"...... the one that drives the driven gear. they used 2 different drive gears in the Muncie's, i believe a 6 tooth for the 4.56, and a 8 tooth for the higher gear sets.
________________________________________ ______________________
You are correct. I looked in the part manual and it is rather confusing :confused: . I could not figure out which was which.
Dave
:cheers:
Thread Starter
Racer
Joined: Aug 2003
Posts: 404
Likes: 0
From: Sitka Alaska
Re: John Z (jimgessner)
Right, page 114 of catalog 1D, 18-20-21-22-24 nylon gears, each tooth changes the speed by approx. 5mph according to CC. Guess I better crawl under the 61 and pull the "bullet" and count teeth/check color of the one now installed. Thanks for the info.
EVERGREEN
EVERGREEN
There is a plastic gear that goes into the side of the transmission and then the speedo cable is screwed into that. Different color gears that have different numbers of gear teeth are used for different rear end ratios.
Go to http://www.corvettecentral.com and ask them for the proer gear. I do not know the color or number of teeth, but they have serviced this part in the past.
[Modified by jimgessner, 10:45 AM 12/31/2003]
Go to http://www.corvettecentral.com and ask them for the proer gear. I do not know the color or number of teeth, but they have serviced this part in the past.
[Modified by jimgessner, 10:45 AM 12/31/2003]
Thread Starter
Racer
Joined: Aug 2003
Posts: 404
Likes: 0
From: Sitka Alaska
Re: John Z (paul67)
Tried the web site you listed but this fancy Gateway computer here at home is really a piece of s*** so got no where, will try Friday on my el cheapo computer at work, it runs circles around this thing.
Thanks,
EVERGREEN
Thanks,
EVERGREEN
This may be helpful.
http://members.core.com/~faldrich/speedo.htm
http://members.core.com/~faldrich/speedo.htm
Thread Starter
Racer
Joined: Aug 2003
Posts: 404
Likes: 0
From: Sitka Alaska
Re: John Z (paul67)
Sorry, its a 61 with 6.70X15 and according to the 1961 Corvette Specifications sheet tire revolutions per mile at 30mph = 760. Also, on the other end, crankshaft RPM @ 1mph with the 4.56:1 = 1st gear =127.2, 2nd gear =96.0, 3rd gear =75.7, and 4th gear = 57.8. Also, there are 8 teeth on the T-10's output shaft. If someone out there is a math wiz (I'm not) perhaps they can use this info and tell me which driven gear would work (or perhaps none will, in which case I will need the box that John Z mentioned).
Thanks,
EVERGREEN
Thanks,
EVERGREEN
If the poster could give us the tire size, we could determine the revs/mile and come down to the correct driven gear. The change in the rear axle is so drastic, however, that he may have to go with a new transmission drive gear as well as the driven gear.
Thread Starter
Racer
Joined: Aug 2003
Posts: 404
Likes: 0
From: Sitka Alaska
Re: John Z (Dave McDufford)
Hey, great picture, and yes I'm familiar with the gear arrangement, and I would like to make this as simple as possible with just changing out that gear but some seem to think (and probably rightfully) that with as much rear gear change (3.36 to 4.56) it might not be possible to be a simple driven gear change for the speedo.
Thanks,
EVERGREEN
Thanks,
EVERGREEN
Below is an image of the part that needs to be replaced and it is called the "Driven Gear". It is the nylon colored gear in the top left of the picture. It is held by the bullet shaped item next to it that is held in the transmission by a small bolt and a clip. The "Driven Gear" is run by the ring shaped gear that is in the lower right of the picture. This gear goes around the output shaft in the tail of the transmission. A 4.56 driven gear can be purchased from LIC for $12.50 part # 32-64D.
Dave
:cheers:
[Modified by Dave McDufford, 5:47 PM 12/31/2003]
Dave
:cheers:
[Modified by Dave McDufford, 5:47 PM 12/31/2003]
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,270
Re: John Z (EVERGREEN)
As previously mentioned I believe the 4.56 ratio had a different internal drive gear, so rather than just a different driven gear, you'll need a Stewart Warner adapter to slow down the speedo.
The ratio (output speed/input speed) should be 3.36/4.56 = .736842.
Select gearing for the box than provides as close as possible to this ratio. You could also go to a speedometer service station where they can test your speedo and come up with a possible better correction because the original gearing and speedo head have a small error.
Duke
The ratio (output speed/input speed) should be 3.36/4.56 = .736842.
Select gearing for the box than provides as close as possible to this ratio. You could also go to a speedometer service station where they can test your speedo and come up with a possible better correction because the original gearing and speedo head have a small error.
Duke
