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Topic: Speedo/Tach Troubles

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Speedo/Tach Troubles (1/23)
 5/26/11 6:20am
manget1Lifetime Member
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Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
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During the Moonshine Cruise during the gathering in Effingham, my speedometer started to freak out.  It had been doing some clicking during our Route 66 trip, then later some bouncing...  During the cruise, it hit 160+ mph then bounced back to normal.

 

Eventually on the drive home, it started to REALLY whine and cranked up to 160 mph consistently Click for Pic. 

 

Shortly after this picture was taken, the needle actually started to bend as if it wanted to go farther (almost like you see in a cartoon) and eventually snapped off!

 

I have replaced the speedo twice in the car.  First time, I bought one off e-bay, had it refurbished and installed it myself.  Within a year, the tripometer on that one was not working, so I had the original one refurbished and had that one installed.  So this is the original that is now out of service.

 

My thought now is to just buy a new one from MAM (glad to give them my business).  Mitch also mentioned a cable lubricator from them (609-467).  He thought that was the issue with why it was squealing in the first place.  I think that route may be cheaper than trying to find another on e-bay and refurbishing (I sold the spare I had on e-bay after re-installing the original).  I also need to understand how set the odometer to the correct mileage once I get the new one.  I figured I'd get a new cable and housing at the same time too.

 

Has anyone ever used these (cable lubricators)?  Is it a permanent install or just an occasional maintenance item.  I list that I also have Tach troubles.  Those issues have also related to the cable (being a 74, my tach runs directly off of a cable from the distributor). 

 

For those of you who have worked on these gauges before, you know what a pain it is.  I want to be DONE with this issue and get it fixed and be able to keep it fixed once and for all!

 

Advice and thoughts requested.



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Speedo/Tach Troubles (2/23)
 5/26/11 8:00am
Adams' AppleLifetime Member
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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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The problem with your speedo is not gonna be the cable...it's the speedo head(gauge) itself. Not saying that the cable might not be in need of some love, but the needle pegging like that is a problem in the head. No way around it...yer gonna have to pull it and replace/repair.
The cable spins a "can" in the head. The "can" has a small magnet in one spot. The needle is attached to a clock-spring(coiled spring) with a ferrous tip on one end. The can/magnet fits over the spring. As the can with the magnet spins, the magnetic attraction of the metal on the spring causes the needle to move, giving you a gauge reading. Sounds like something has gotten between the can and the spring assy, causing it to be "direct drive"....not gud...


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Speedo/Tach Troubles (3/23)
 5/26/11 5:18pm
rraider1
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Woodland, WA - USA

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1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion


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Speedo/Tach Troubles (4/23)
 5/27/11 5:38am
manget1Lifetime Member
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Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

Thanks guys.  Joel, your explanation makes more sense, especially since I forgot to mention one little detail - the odometer still appears to be working (and appeared to work correctly during the 160+ time.
 
Sounds like a replacement speedo is on the way...


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Speedo/Tach Troubles (5/23)
 5/27/11 11:24am
The RookLifetime Member
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Pittsburgh, PA - USA

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1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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Not to hijack the thread, but while on this subject, I too have a speedo issue, mine works, but the speed reading is off about 10 MPH. My trip odomomter doesnt work my regular odometer does work,  but it too is out of calibration judging by me tracking mile markers on the highway. Is one related to the other (probably right?) but which one? So I was planning to send out the entire speedo to be rebuilt. Do you think that will solve these issues too....
Speedo/Tach Troubles (6/23)
 5/27/11 11:44am
rraider1
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Woodland, WA - USA

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A couple of simple things to look at. on my 77 to change the trip meter you pull down and turn to reset to 000 if you do not push it back up it does not work, as to accuracy mine is about 5 mph off but I beleive it is do to the tire size on the rear wheels.
Their may be some old threads on the tire size issue
 
Speedo/Tach Troubles (7/23)
 5/27/11 12:58pm
eboLifetime Member
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Holland Patent, NY - USA

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HIJACK..........Dan,
Robert is right the tires size will change it some, check that.
I think you may have the wrong spedo gear in the cable. You can easily get under the car ....ok well nobody can easily get under the car.....  unscrew the cable going into the tranny and look at the color of that gear, different colors for different ratios. Someone,  Joel for sure should know what color it should be. Then go out and check it like we did running down the road with someone. You seemed to be off exactly 10 mph......but at least it was under and not over. "Well you see officer my spedo said I was doing 80 but actually I was only doing 70, you see my gear is the wrong color and I need a pink one.....it's so hard to find parts for theses cars you understand right......Yes sir....well no sir.....ok sir , I understand sir, drivers license, registration, and insurance card....right away sir" EmbarrassedLOLLOL
Evil Smileebo
ebo2011-05-27 10:09:35

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Speedo/Tach Troubles (8/23)
 5/27/11 1:03pm
The RookLifetime Member
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Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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Rolling On The Floor LaughingRolling On The Floor Laughing
God I hope I dont need the pink one....Ebo would never let me live that down....
Speedo/Tach Troubles (9/23)
 5/27/11 1:17pm
eboLifetime Member
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Holland Patent, NY - USA

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   Hijack.............
Sorry there is no "PINK" your safe
Evil Smileebo
ebo2011-05-27 10:18:39

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Speedo/Tach Troubles (10/23)
 5/27/11 1:25pm
The RookLifetime Member
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Pittsburgh, PA - USA

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1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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Whew!!!!!!
Speedo/Tach Troubles (11/23)
 5/27/11 9:02pm
manget1Lifetime Member
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Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

I don't know who this "Jack" fellow is, but I'll join the crowd and welcome him too.  Hi Jack!
 
I agree with rraider.  I've had troubles before with my trip not working and then found I really had to pull down to get it to go...


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Speedo/Tach Troubles (12/23)
 5/27/11 9:09pm
eboLifetime Member
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Holland Patent, NY - USA

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[QUOTE=manget1] Hi Jack! I really had to pull down to get it to go...[/QUOTE]
 
Hmmmm is this sumthin that should be written in a little book???LOL
Evil Smileebo


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Speedo/Tach Troubles (13/23)
 5/27/11 9:11pm
Jaws79Lifetime Member
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Sykesville, MD - USA

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Yeah, but 79s have a push button reset on the trip odometer! Mine actually resets to just below 0 ( sounds wierd, I know ). But it works!
 
Barry
 
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Speedo/Tach Troubles (14/23)
 5/27/11 9:50pm
The RookLifetime Member
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Pittsburgh, PA - USA

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1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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[QUOTE=ebo][QUOTE=manget1] Hi Jack! I really had to pull down to get it to go...[/QUOTE]
 
Hmmmm is this sumthin that should be written in a little book???LOL
Evil Smileebo
[/QUOTE]
i didnt seem to make the little book......yet!!Rolling On The Floor Laughing
Marshall..youre gonna need a bigger book......
The Rook2011-05-27 18:51:57
Speedo/Tach Troubles (15/23)
 5/28/11 7:28am
manget1Lifetime Member
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Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

Duly noted!!
 
The list should make it here to the site this weekend


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Speedo/Tach Troubles (16/23)
 5/30/11 8:04am
manget1Lifetime Member
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Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

[QUOTE=manget1]Duly noted!!
 
The list should make it here to the site this weekend
[/QUOTE]
The list is now posted...  https://www.c3vr.com/forum/topic82036_post386338.html#386338

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I wanted a Corvette my whole life, but I never dreamed of all the wonderful people I would meet because of it!


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Speedo/Tach Troubles (17/23)
 5/31/11 10:25pm
The RookLifetime Member
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Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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Posts: 600

I did indeed realize today that my original rally wheel tires were 225's and my new aluminum rim tires are 255's. Im guessing this is why theres a difference.....so how do I remedy that oh great gods of the C3's? (without changing the tires ebo...)

Speedo/Tach Troubles (18/23)
 5/31/11 10:56pm
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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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Change the driven speedo gear....or put a reducer on the cable, if it doesn't already have one. The pic of the gear Albo posted above is incorrect for a 350, but correct for a 400 or 700. Assuming you still have the original trans in yer car, it should be a 400 w/L-82. Take your gear out and count the teeth...then get one with aboot 2-3 teeth LESS to speed the speedo up. Color is really irrelevant anymore, but might be helpful in determining which gear you have. The large gears like is pictured above will also have the tooth count embossed in it.Tongue




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Joel Adams
C3VR Lifetime Member #56    

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(click for Texas-sized view!)
             NCRS

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Speedo/Tach Troubles (19/23)
 5/31/11 11:50pm
VetteCountryLifetime Member
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Belvidere, IL - USA

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One tooth=3mph.
Speedo/Tach Troubles (20/23)
 6/2/11 5:47pm
The RookLifetime Member
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Pittsburgh, PA - USA

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1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


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Posts: 600

[QUOTE=Adams' Apple]Change the driven speedo gear....or put a reducer on the cable, if it doesn't already have one. The pic of the gear Albo posted above is incorrect for a 350, but correct for a 400 or 700. Assuming you still have the original trans in yer car, it should be a 400 w/L-82. Take your gear out and count the teeth...then get one with aboot 2-3 teeth LESS to speed the speedo up. Color is really irrelevant anymore, but might be helpful in determining which gear you have. The large gears like is pictured above will also have the tooth count embossed in it.Tongue


[/QUOTE]
But I need to slow the speedo down its reading 10 mph faster than Im going...so I want 2 or 3 less teeth...right????
Speedo/Tach Troubles (21/23)
 6/2/11 5:48pm
The RookLifetime Member
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Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......


Joined: 12/4/2002
Posts: 600

[QUOTE=Adams' Apple]Change the driven speedo gear....or put a reducer on the cable, if it doesn't already have one. The pic of the gear Albo posted above is incorrect for a 350, but correct for a 400 or 700. Assuming you still have the original trans in yer car, it should be a 400 w/L-82. Take your gear out and count the teeth...then get one with aboot 2-3 teeth LESS to speed the speedo up. Color is really irrelevant anymore, but might be helpful in determining which gear you have. The large gears like is pictured above will also have the tooth count embossed in it.Tongue


[/QUOTE]
But I need to slow the speedo down its reading 10 mph faster than Im going...so I want 2 or 3 more teeth...right????
Speedo/Tach Troubles (22/23)
 6/2/11 10:24pm
Adams' AppleLifetime Member
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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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Whut?

If you have tires that are taller(255 vs. 225) than original, the speedo would be slower than actual speed. Ermm

Either way...changing the driven gear will get you so far in either direction...more toofers= slow it down, less toofers= speed it up. You can only go so far, however, before you'll need to change the driven gear inside the trans.


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Joel Adams
C3VR Lifetime Member #56    

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(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"

Speedo/Tach Troubles (23/23)
 6/3/11 6:19am
lukesvetteLifetime Member
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HOWELL, NJ - USA

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1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.


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[QUOTE=Adams' Apple]Whut?

If you have tires that are taller(255 vs. 225) than original, the speedo would be slower than actual speed. Ermm

Either way...changing the driven gear will get you so far in either direction...more toofers= slow it down, less toofers= speed it up. You can only go so far, however, before you'll need to change the driven gear inside the trans.
[/QUOTE]

 Hi Jack!!

Changing the gear on the output shaft is a PITA!! Hopefully you only need to go a couple of teeth on the driven gear. I have a bunch of them - if you let me know which one you need, I'll mail it you ya iffins I got it!!

Paul
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